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Glossary of Nautical and Sailing Terms and Abbreviations

Navigating the waters of nautical and sailing terminology can be as challenging as sailing through uncharted waters. This comprehensive glossary covers essential terms and abbreviations, providing a valuable resource for both seasoned sailors and landlubbers alike. The terms are organized alphabetically for easy reference.

Aback : When a sail is aback, the wind fills it from the wrong side, pushing it against the mast. This is often unintended and can hinder forward motion.
Abaft : Toward the stern (rear) of the boat, relative to some object or position (“abaft the mast”).
Abaft the Beam : A direction behind a line drawn at right angles to the ship’s keel (more toward the stern than the beam).
Abandon Ship : A command to leave the vessel immediately, usually in the face of imminent danger.
Abeam : At right angles to the keel of the ship; directly off the side of the vessel.
Aboard : On or within the ship; “close aboard” means near the ship.
Above Board : Referring to actions or behavior that are honest and open.
Accommodation : Quarters or rooms for passengers or crew on a ship.
Accommodation Ladder : A portable flight of steps down a ship’s side, used for boarding or disembarking.
Admiral : A senior naval officer of high rank, typically commanding a fleet or group of ships.
Admiralty : The authority responsible for the command of a navy.
Admiralty Chart : An official nautical chart issued by the Admiralty (British maritime authority).
Admiralty Law : A body of law that governs maritime matters and offenses.
Adrift : Floating without being moored or steered; not under control.
Aft : Toward the stern (rear) of the vessel.
After Bow Spring Line : A mooring line running forward from the stern to the dock.
Aftcastle : A superstructure at the stern of a vessel.
Aground : Resting on or touching the ground or the bottom of a body of water.
Ahead : In the forward direction; in front of the vessel.
Ahoy : A call used in hailing a ship or boat.
A-hull : To ride out a storm with no sails and the helm lashed to leeward.
Aid to Navigation (ATON) : Any device external to a vessel intended to assist navigators in determining their position or safe course, or to warn of dangers or obstructions.
Airdraft : The distance from the waterline to the highest point on a vessel.
AIS (Automatic Identification System) : A tracking system used on ships and by vessel traffic services for identifying and locating vessels.
Albatross : A large seabird; considered a sign of good luck by sailors.
All Hands : The entire crew of a ship.
Allision : The running of one ship upon another ship that is stationary.
Alongside : By the side of a ship or pier.
Aloft : Above the deck, in the rigging or mast.
Amidships : In the middle portion of the ship, along the line of the keel.
Anemometer : An instrument for measuring wind speed.
Anchor : A device used to secure a vessel to the bed of a body of water.
Anchor Ball : A black ball displayed in the forepart of a vessel to show that it is anchored.
Anchor Buoy : A small buoy used to mark the position of an anchor.
Anchor Chain or Cable : The chain or line connecting a vessel to its anchor.
Anchor Detail : The crew members who handle the anchoring equipment during anchoring operations.
Anchor Light : A white light displayed by a ship at anchor to signal its position at night.
Anchor Rode : The line or chain that connects the anchor to the vessel.
Anchor Watch : A watch kept while the ship is at anchor to ensure it is not dragging.
Anchorage : A suitable place where a ship can anchor safely.
Anchor’s Aweigh : The anchor is clear of the sea bottom and the ship is free to move.
Apparent Wind : The wind experienced on a moving vessel, a combination of the true wind and the wind created by the vessel’s motion.
Apron : The deck or area immediately in front of the entrance to the cabin.
ARPA (Automatic Radar Plotting Aid) : A system for tracking other vessels using radar data to assist in collision avoidance.
Armament : The weapons carried by a ship for defense or combat.
Ashore : On or towards the shore.
Asylum Harbor : A harbor where vessels may seek shelter from storms.
Astern : Behind or toward the rear of a ship; moving in reverse.
Athwart, Athwartships : Across the ship from side to side; perpendicular to the keel line.
Auxiliary Engine : A secondary engine used for generating power or for emergency propulsion.
Auxiliary Vessel : A ship designed to support the operations of combatant ships and other naval activities.
Avast : A command meaning stop or cease immediately.
Awash : So low in the water that the water is constantly washing across the surface.
Aweigh : Just clear of the sea bottom when hoisting the anchor.
Aye, Aye : A response indicating that an order is understood and will be carried out.
Azimuth : The direction of a celestial object from the observer, expressed as the angular distance from the north point of the horizon.
Azimuth Circle : A device used with a compass to take bearings of celestial or terrestrial objects.
Azimuth Compass : A compass equipped with an azimuth circle for taking precise bearings.
Back and Fill : A maneuver using the tide’s advantage when the wind is not favorable, typically in narrow channels or during docking.
Backstays : Cables or lines extending from the ship’s stern to the masthead, providing support and stability to the mast.
Baggywrinkle : A soft covering, usually made from old rope, wrapped around rigging cables to prevent sail chafing.
Ballast : Material placed in the lower part of a boat or ship to provide stability and improve handling and balance.
Ballast Tank : A compartment within a boat or ship that holds water to provide stability.
Bar : A large mass of sand or earth formed by sea surges, often found at river mouths or harbor entrances, affecting navigation.
Bar Pilot : A specialist navigator who guides ships through challenging areas like sandbars or river mouths.
Barque : A sailing vessel with three or more masts, with square sails on all but the aftmost mast.
Barometer : An instrument measuring atmospheric pressure, used in forecasting weather.
Barrelman : A sailor stationed in the crow’s nest, responsible for lookout duties and spotting hazards or other ships.
Batten : A thin, flexible strip inserted into the sail’s edge, providing stability and shape to the sail.
Batten Down : To secure the ship’s hatches and gear before bad weather.
Beam : The widest part of a boat, crucial for stability.
Bear Away/Down : Steering a vessel away from the wind.
Bearing : The direction or position of an object, typically another vessel, relative to one’s own position, measured in degrees.
Becalm : To render a ship motionless due to lack of wind.
Before the Mast : Referring to the living quarters of enlisted sailors, located in the front part of the ship.
Belaying Pins : Rods or bars used to secure ropes or rigging on a ship.
Bell Buoy : A buoy with a bell that rings due to the motion of the waves, used as a navigational aid.
Berth : A sleeping compartment on a boat, or a designated space in a harbor where a vessel can be moored.
Best Bower : The larger of two anchors on a ship, often the primary anchor used for securing the vessel.
Bilge : The lowest part of a boat’s interior, where water typically collects and needs to be pumped out.
Bilge Keel : A fin-like structure on either side of a ship’s hull, reducing rolling and providing stability.
Bilge Pump : A mechanical or manual device used to remove water accumulated in the bilge.
Bimini : A protective covering, typically made of weather-resistant fabric, mounted over a boat’s cockpit to shield from sun or rain.
Binnacle : A stand or housing on a ship that holds navigational instruments, including the ship’s compass.
Bitter End : The final part of a rope or anchor cable.
Bitts : Strong vertical posts on a ship’s deck for fastening ropes or cables.
Block : A pulley used in sailing to change the direction of a line or increase mechanical advantage.
Boat Hook : A pole with a hook on the end, used for pushing or pulling boats or retrieving objects from the water.
Boatswain (or Bosun) : A ship’s officer in charge of equipment and the crew.
Boom : A horizontal pole attached to the mast, used to extend and control the foot of a sail.
Boom Vang : A device used on sailboats to control the angle and tension of the boom, influencing sail shape and performance.
Bow : The front or forward part of a boat.
Bow-Chaser : A type of long gun placed at the front of a ship, used for firing directly ahead, especially useful in naval pursuits.
Bowline : A type of knot creating a fixed loop at the end of a rope, known for its strength and stability.
Bow Thruster : A propulsion device built into, or mounted to, the bow to make a vessel more maneuverable.
Bowsprit : A spar extending forward from a ship’s bow, used to support fore-sails and increase sail area.
Breakwater : A structure built to protect a shore or harbor from the force of waves.
Bridge : The area on a ship where the command and navigation are conducted.
Brig : A two-masted sailing vessel with square sails on both masts; also refers to a ship’s jail.
Broaching-To : A sudden veering or turning of a ship, often causing it to face into the wind or waves, potentially dangerous in heavy seas.
Bulk Carrier : A ship designed to transport unpackaged bulk cargo such as grains, coal, ore, and cement.
Bulkhead : A structural partition within a ship, dividing various compartments for stability and safety.
Bulwark : The extension of a ship’s sides above the level of the deck, providing protection against waves.
Bunkering : The process of supplying a ship with fuel.
Burgee : A small flag used to indicate a vessel’s yacht club membership or to serve as a wind indicator.
Buoy : A floating device used to mark specific points in the water, such as hazards, channels, or anchoring locations.
Buoyancy : The ability of an object to float in water or fluid due to the upward force exerted by the fluid.
By the Lee : Sailing with the wind coming from behind the boat on the same side as the boom, which can risk an accidental jibe.
Cabin : Enclosed living space on a boat, offering shelter and accommodations. It can range from basic to luxurious, depending on the vessel.
Cable : A large rope or a measure of distance at sea, often used in anchoring or mooring a vessel. It is crucial in various maritime operations.
Cable’s Length : A nautical unit of measure equal to one-tenth of a nautical mile (approximately 185.2 meters or 607 feet).
Capsize : The act of a boat turning over in the water, which can be accidental or due to extreme conditions. Capsizing is a critical concern in boating safety.
Cardinal Points : The four main points of the compass—North, East, South, and West—used for navigation.
Cast Off : To let go or release (a line or a mooring) when departing from a dock or another vessel.
Catamaran : A boat with two parallel hulls, offering stability and space. It’s popular for both recreational and racing purposes.
Celestial Navigation : The use of positions of stars, planets, the sun, and the moon to determine one’s position at sea.
Centreboard : A retractable keel that moves vertically, used to reduce sideways movement (leeway) in sailing boats.
Chart : A nautical map used for navigation, showing depths, navigation hazards, and other important features.
Chart Datum : A reference level on nautical charts, indicating the lowest tide level. It’s essential for safe navigation, especially near shorelines.
Chock : A metal fitting through which mooring lines are passed, used to guide and protect the lines.
Cleat : A fitting, often made of metal or plastic, used for securing ropes on a boat. It’s fundamental hardware for mooring and rigging.
Cleat Hitch : A method of securing a line to a cleat, ensuring it stays fastened under load.
Clew : The lower aft corner of a sail, where the foot and leech intersect. It plays a crucial role in controlling sail shape.
Clipper : A fast sailing ship of the 19th century, known for its speed and used primarily for trade.
Close-Hauled : Sailing as close to the wind as possible without stalling. It’s a challenging point of sail requiring precise control.
Coaming : A raised border around a deck opening, such as a hatch, to prevent water from entering.
Cockpit : The area, usually lower than the deck, where the boat’s controls are located. It’s the primary operating station for steering and maneuvering.
Companionway : The set of steps or a ladder leading from the boat’s deck down to the cabin. It serves as the main entry to the interior.
Course : The intended direction of travel of a vessel over the ground.
Coxswain : The person who steers a boat, especially in smaller vessels or lifeboats.
Cringle : A reinforced eyelet, often found at the ends of reef lines or on sails, used for securing or adjusting the sail.
Crow’s Nest : A lookout point positioned high on a ship’s mast, used for observation and spotting hazards or other ships.
Cutter : A small, single-masted sailing vessel, fore-and-aft rigged, with two or more headsails.
Daggerboard : A vertically movable fin in smaller sailboats, providing stability and controlling side-slippage.
Davit : A small crane on board a ship, used to lower and raise boats, anchors, or cargo.
Davy Jones’ Locker : Nautical folklore for the seabed, symbolizing the final resting place of drowned sailors.
Daybeacon : An unlit navigation marker, visible in daylight, used for identifying locations or hazards.
Deadeye : A round wooden block with holes, part of a ship’s standing rigging, used for tensioning shrouds.
Dead Reckoning : The process of calculating one’s current position by using a previously determined position and advancing that position based upon known speed, elapsed time, and course.
Deadrise : The angle formed between the boat’s bottom and a horizontal plane, important for understanding hull design.
Deck : The top surface of a boat’s hull where crew and passengers stand.
Deckhand : A crew member responsible for general work on the main deck.
Deep Six : A term meaning to discard or dispose of something, originating from throwing items overboard into deep water.
Derrick : A lifting device on ships, composed of a mast or pole and a boom, used for cargo handling.
Devil Seam : A particularly difficult seam to seal on a ship’s hull, located near the waterline.
Dinghy : A small boat, often used for short trips or as a tender for larger vessels.
Displacement : The weight of water displaced by the submerged part of a ship, equal to the weight of the ship itself.
Dock : A structure extending alongshore or out from the shore into a body of water, to which boats may be moored.
Dog Watch : A shorter than usual watch period on ships, typically two hours, to rotate duty times and adjust the crew’s schedule.
Dolphin : A man-made marine structure of piled beams used for mooring vessels or as a navigational aid.
Downhaul : A rope or line used for adjusting the tension on a sail or spar.
Draft : The vertical distance from the waterline to the lowest point of a ship’s keel, important for determining navigable water depth.
Dredging : The removal of sediments and debris from the bottom of water bodies to deepen them for navigation, environmental cleanup, or land reclamation.
Drift : The leeway or movement of a vessel downwind or downstream due to wind or current.
Drifter : A light sail used in gentle wind conditions to increase a sailing vessel’s speed.
Drogue : A device trailed behind a boat to slow it down, particularly useful in heavy weather to control speed and maintain stability.
Dry Dock : A dock that can be drained of water to allow maintenance and repairs to the hull of a ship.
Ease Sheets : To let out a sail’s sheet (control line) to reduce wind pressure and speed.
Easting : Progressing eastward; used in navigation to indicate the distance traveled or required to reach a destination to the east.
Ebb Tide : The period when the tide level is falling; the outgoing tide.
Echo Sounder : An instrument used to measure the depth of water beneath a ship by sending sound pulses and timing their return.
Earrings : Ropes used to secure the top corners of large sails to the yardarms, essential in sail management.
Embayed : A situation where a vessel is trapped between headlands, often with winds blowing onshore, posing navigational challenges.
Engine : The power unit used to propel a boat, varying in type and size depending on the vessel.
Ensign : A flag flown by a ship to indicate its nationality.
EP (Estimated Position) : A navigational term referring to the calculated location of a vessel based on estimations.
EPIRB (Emergency Position Indicating Radio Beacon) : A crucial safety device that sends out a distress signal in emergencies, helping in the location of vessels in distress.
ETA (Estimated Time of Arrival) : The predicted time a vessel is expected to arrive at a destination. Read more: What Is ETA and ETD in Shipping?
ETD (Estimated Time of Departure) : The planned time for a vessel’s departure from a port or location. Read more: What Is ETA and ETD in Shipping?
Estuary : A water passage where the tide meets a river current; an inlet or arm of the sea at the lower end of a river.
Even Keel : Refers to a condition where a boat or ship is perfectly balanced in the water, not tilting to either side. This balance is crucial for optimal performance and safety, ensuring the vessel moves efficiently and remains stable.
Extremis : A critical point in navigation rules where vessels in danger of collision must take action to avoid it.
Eye Bolt : A bolt with a looped head, used for attaching lines or cables.
Eye of the Wind : The direction from which the wind is blowing; sailing directly into the wind.
Eye Splice : A method of creating a permanent loop at the end of a rope by splicing.
Fairlead : A fitting that guides ropes smoothly, preventing friction and wear.
Fairway : A navigable channel in a river or harbor, safe for ships to travel.
Fathom : A unit of depth measurement in maritime contexts, equal to six feet. Read more about fathom as a nautical measurement .
Fathometer : An instrument used to measure the depth of water beneath a ship; also known as an echo sounder.
Fender : A cushioning device, often air or foam-filled, used to prevent a boat from damaging itself or other objects. Read more about boat fenders and bumpers .
Figurehead : A decorative carved figure located at the front of older sailing ships.
Fireboat : A specialized vessel equipped to fight fires on other vessels or waterfront structures.
Fireship : Historically, a ship filled with combustibles and set on fire, used as a weapon to destroy enemy ships.
First Mate : The officer second in command to the captain, responsible for the ship’s cargo and deck crew.
First Rate : A classification for the largest and most heavily armed warships from the 17th to 19th centuries.
Flag Hoist : A series of signal flags strung together to convey messages between ships.
Flag Officer : A senior naval officer entitled to fly a flag to mark the ship or headquarters from which they exercise command.
Flare : An emergency signaling device emitting bright light, used for distress signaling at sea.
Fleet : A group of ships sailing together, engaged in the same activity, or under the same ownership.
Flotsam : Debris or wreckage of a ship found floating on the sea; often refers to cargo or equipment lost overboard.
Fluke : The wedge-shaped part of an anchor’s arm, essential for securing the anchor in the seabed. Learn more about fluke-style anchors .
Fo’c’sle (Forecastle) : A section at the front of a ship, traditionally housing crew quarters.
Fore : Toward the front or bow of a vessel.
Fore and Aft : Along the length of a ship, from the bow (front) to the stern (rear).
Foremast : The mast nearest the bow in a ship with more than one mast.
Foresail : The lowest sail on the foremast of a square-rigged vessel; on a fore-and-aft rigged vessel, the sail set forward of the mainmast.
Forward : Toward the front end of the ship.
Freeboard : The distance from the waterline to the upper deck level, measured at the lowest point where water can enter the boat or ship.
Furl : To roll or wrap a sail around a spar or mast, a common practice in managing sails.
Full and By : Sailing close-hauled, making the best possible speed while keeping the sails full.
Gaff : A spar supporting the upper side of a fore-and-aft sail, essential in traditional sail configurations.
Galley : The kitchen area on a boat, equipped for cooking and preparing meals.
Galley Slave : A person, often a prisoner or slave, who was forced to row in a galley, especially during the 16th to 19th centuries.
Gangplank : A movable bridge allowing passengers and crew to board or leave a ship, especially at a pier.
Gangway : An opening in the ship’s side or bulwarks by which people can enter or leave the vessel; also a command to clear the way.
Garboard : The bottom plank of a boat’s hull, adjacent to the keel, playing a critical role in hull integrity.
Garboard Strake : The first range of planks or plates laid on a ship’s hull next to the keel.
Gasket : A cord or canvas band used to secure a furled sail to the yard or boom.
General Average : A maritime law principle where all parties in a sea venture proportionally share any losses resulting from a voluntary sacrifice of part of the ship or cargo to save the whole in an emergency.
Genoa : A large jib or foresail, often overlapping the mainsail, used for improved sailing efficiency, especially in lighter winds.
Gig : A light, fast, narrow boat designed for speed, often used for transport between a ship and shore.
Gimbal : A pivoting support allowing an object to remain level regardless of the boat’s motion, commonly used for compasses and cooking appliances.
Give-Way Vessel : The vessel that must yield to another vessel under navigation rules to avoid collision.
Globe Valve : A type of valve used for regulating flow in a pipeline aboard a ship.
Gooseneck : A swivel joint between the boom and the mast that allows the boom to move freely.
GPS (Global Positioning System) : A satellite-based navigation system providing location and time information globally, vital for modern navigation.
Grab Rails : Hand-hold fittings mounted on cabin tops or sides for personal safety when moving around the boat.
Grapeshot : A type of ammunition used in naval warfare, consisting of small metal balls, effective against personnel rather than structures.
Ground Tackle : A collective term for all the equipment used in anchoring a ship, including anchors, chains, and associated fittings.
Gudgeon and Pintle : Components of the hinge mechanism connecting the rudder to the boat, crucial for steering.
Gunkholing : Cruising in shallow or shoal water, exploring coves and anchorages, often in remote or secluded areas.
Gunwale (pronounced ‘gunnel’) : The upper edge of the side of a boat, providing structural integrity and support.
Guy : A rope or line used to control the movement of a sail or spar, especially to prevent unwanted movement.
Gybe (or Jibe) : A sailing maneuver where the boat turns so its stern passes through the wind, changing direction while sailing downwind.
Halyard (or Halliard) : A line used to hoist a sail’s head or a spar; essential for sail manipulation.
Hammock : A canvas bed slung from a ship’s deckhead, used for sailors’ sleeping quarters.
Hand Bomber : Historical term for a ship with manually shoveled coal-fired boilers.
Hand over Fist : Expression describing steady upward climbing, akin to a sailor ascending a ship’s shrouds.
Handsomely : Slow, steady motion, especially when hauling a line.
Hank : A fitting used to connect a sail’s luff to a stay, typically featuring a spring-operated gate or snap fastener.
Harbor (or Harbour, Haven) : A natural or man-made shelter for ships, providing protection from weather.
Haul Wind : Sailing towards the wind’s direction, not the fastest sailing point.
HAT (Highest Astronomical Tide) : The highest level of tide predicted under average meteorological conditions.
Hatch : An opening in a ship’s deck for interior access.
Hawse-hole : A hole in the ship’s bow for anchor cables or chains.
Hawsepiper : A maritime officer who started as an unlicensed seaman without formal maritime education.
Head : The toilet or latrine on a vessel, traditionally positioned at the bow.
Head of Navigation : The farthest navigable point on a river for ships.
Head-to-Wind : Position where a boat’s bow points directly into the wind.
Headfoil : A streamlined cover around a forestay, with a groove for a headsail’s luff.
Heads : Toilets on a boat.
Headsail : Any sail flown in front of a vessel’s foremost mast.
Headway : Forward movement of a boat through water.
Heave : A vessel’s temporary vertical motion, up and down.
Heave Down : Tilting a ship on its side, often for cleaning purposes.
Heave-to : A maneuver in heavy weather to reduce a boat’s headway by backing the jib and lashing the tiller to leeward.
Heaving to : Stopping a sailing vessel by opposing the helm and sails, causing a leeward drift.
Heel : The action of a boat leaning to one side.
Heeling : The leaning of a sailing vessel caused by wind pressure on its sails.
Helm : The wheel or tiller used to steer a ship.
Helmsman : Person responsible for steering a ship.
Hogging (or Hog): Hull distortion where the keel’s ends are lower than the center. Read more about hogging and sagging in ships .
Hold : The lower part of a ship’s interior, used for storage, such as cargo.
Holiday : An unintentional gap in the application of paint or other preservative substances.
Holystone : Sandstone block used for scrubbing a ship’s deck.
Horn : A sound signal device powered by electricity or compressed air.
Horse : Attachment for sheets on a vessel’s deck.
Hounds : Attachments for stays on masts.
Hull : The shell and structural framework of a ship’s basic flotation section.
Hydrofoil : A boat with underwater wings or foils for lift and speed enhancement. Read more about hydrofoil boats .
Icebreaker : A ship designed to navigate and break through ice-covered waters, enabling travel in polar regions. Read more about how icebreakers work or the top 10 biggest icebreakers in the world .
Icing : A hazardous condition where sea spray freezes upon contact with the ship in cold temperatures (below about -10°C) and high wind speeds (force 8 or above on the Beaufort scale).
Idlers : Members of a ship’s crew who are not required to stand watches, typically specialist tradesmen like carpenters and sailmakers.
IMO (International Maritime Organisation) : A specialized agency of the United Nations responsible for regulating shipping.
Impeller : A rotating component in a pump or engine, used to move water for cooling or propulsion.
In Irons : A sailing term for when a boat’s bow is into the wind, causing it to stall and lose maneuverability.
In the Offing : Originally meaning in the waters visible from onboard a ship, now refers to something imminent or about to happen.
Inboard Motor : An engine mounted inside the boat, typically below the deck, used for propulsion.
Inboard-Outboard Drive System : A hybrid marine propulsion system combining features of inboard and outboard motors, often found in larger powerboats.
Inclinometer : An instrument used on ships to measure the degree of tilt or inclination, showing the vessel’s angle relative to the horizontal.
International Date Line : An imaginary line on the Earth’s surface defining the boundary between one day and the next, affecting time zones and navigation.
International Maritime Law : A body of laws, conventions, and treaties governing international private business or other matters involving ships and shipping.
International Waters : Areas of the sea not under the jurisdiction of any country, open for navigation by all nations.
IRPCS (International Regulations for Preventing Collisions at Sea) : A set of international rules governing navigation to prevent collisions between vessels at sea.
Isobars : Lines on a weather map joining places of equal atmospheric pressure, crucial for weather prediction and navigation.
Isobath : Lines on a chart that connect points of equal depth below water, important for safe navigation and understanding underwater topography.
ITF (International Transport Workers’ Federation) : A global union federation representing transport workers, including seafarers, advocating for fair working conditions and rights.
ITU (International Telecommunication Union) : A United Nations specialized agency for information and communication technologies, including maritime communications.
Jack : In nautical terms, it refers to either a flag, specifically flown at the jackstaff at the bow of a ship, or colloquially to a sailor.
Jack Tar : A term for a sailor, historically dressed in ‘square rig’ with a square collar and sometimes a tarred pigtail.
Jacklines or Jack Stays : Lines, often steel wire with a plastic coating, running from bow to stern on both sides of a ship, used for clipping on safety harnesses to secure crew while allowing deck mobility.
Jacob’s Ladder : A rope ladder with wooden rungs used to allow access over the side of a ship.
Jetsam : Goods thrown overboard deliberately to lighten the load of a ship in distress.
Jetty : A structure projecting into the sea, harbor, or river from the shore, used to protect a harbor or influence the current.
Jettison : To throw goods overboard to lighten the load in an emergency.
Jib : A triangular staysail set at the front of a ship, important for its maneuvering and speed.
Jibboom : A spar used to extend the bowsprit, allowing for additional headsails.
Jibe (or Gybe) : A sailing maneuver where the stern of the boat turns through the wind, changing the side of the boat the sail is on.
Jigger-Mast : The fourth or rearmost mast on a ship, generally the smallest on vessels with fewer than four masts.
Jolly Boat : A small workboat or tender carried by a ship.
Jollies : A traditional Royal Navy nickname for the Royal Marines.
Jonah : A person or thing that is believed to bring bad luck, especially aboard ship.
Junk : Old, unusable cordage on a ship, often repurposed by teasing apart strands in a process called picking oakum.
Jury : Refers to a temporary replacement for lost or damaged gear on a ship, often improvised in emergencies.
Keel : The primary structural element of a boat’s hull, extending along the bottom and often protruding into the water for stability.
Keelhauling : A severe maritime punishment involving dragging a person under the keel of a ship.
Keelson (or Kelson) : A timber placed immediately above the keel inside a wooden ship, contributing to the hull’s structural integrity.
Kedge : A small, light secondary anchor used for additional anchoring or maneuvering.
Ketch : A two-masted sailing vessel with a mainmast and a smaller mizzenmast, the latter stepped forward of the rudder post.
Kicking Strap (or Boom Vang) : A line or tackle used to control a sailboat’s boom position, pulling it down to maintain a horizontal orientation, especially useful on a reach or run.
Killick : A small anchor, symbolically representing a non-commissioned officer in the Royal Navy, or used colloquially to refer to an able seaman skilled in anchor handling.
King Plank : The center plank running down the middle of a wooden deck, important for structural integrity.
Kingpost : A strong vertical post used in ship construction to support decks or used in cargo handling to support cargo booms.
Kissing the Gunner’s Daughter : A naval punishment where a sailor was bent over a cannon’s barrel for a spanking with a cane or cat-o’-nine-tails.
Kite : A colloquial term for a spinnaker, a large, lightweight sail used when sailing downwind.
Knee : An angled piece of wood or metal used to strengthen the joints between the sides and deck of a wooden ship.
Knarr : A type of Norse merchant ship used during the Viking Age for long sea voyages.
Knot : A unit of speed equal to one nautical mile per hour, commonly used in maritime contexts.
Knotmeter : An instrument used to measure the speed of a vessel through the water in knots.
Know the Ropes : A phrase indicating thorough familiarity with the ropes and cordage necessary for operating a ship.
Knuckle : A sharp change in direction in a ship’s hull or deck, often where the hull shape changes.
Ladder : On ships, most ‘stairs’ are called ladders, typically narrow and nearly vertical.
Laker : A vessel that operates exclusively on the Great Lakes.
Land Lubber : A person inexperienced or unfamiliar with the sea and sailing.
Lanyard : A short line used to secure or tether an object, such as a tool, to prevent loss.
Larboard : Archaic term for the left side of a ship, now known as ‘port’.
Large (By and Large) : Nautical term referring to sailing both with and against the wind.
Latitude : The angular distance north or south from the Earth’s equator, measured in degrees.
LAT (Lowest Astronomical Tide) : The lowest level that sea tides can reach, used as a reference in charting.
Lateral System : Navigation aids system indicating the sides of channels relative to a conventional direction. Read more about Lateral Markers: Guide to Navigating Safely .
Launch : To set a boat or ship afloat; also, a small open motorboat.
Lay : Orders related to crew movement or ship’s course; also, the twisting of rope strands.
Lay Down : To begin ship construction in a shipyard.
Lazy Jacks : Lines or ropes used to assist in controlling a sail when lowering or reefing.
League : A unit of distance, often equated to three nautical miles.
Lee : The side of the boat sheltered from the wind.
Lee Helm : Tendency of a boat to bear away from the wind, requiring the helm to be pushed leeward to maintain a straight course.
Lee Shore : A shore onto which the wind blows, posing a risk for ships being blown aground.
Leech : The after edge of a sail, particularly susceptible to twist and controlled by the vang and mainsheet.
Leeward : The direction toward which the wind is blowing.
Leeway : The sideways movement of a ship off its course due to wind pressure.
Let Go and Haul : An order indicating alignment with the wind.
Letter of Marque and Reprisal : A government license authorizing a privateer to attack enemy ships.
Lifeboat : A small, sturdy boat carried on ships, used for emergency evacuation.
Lifeline : A safety line or cable running along the sides of a boat.
Liferaft : An inflatable raft used for emergency abandonment of a ship.
Line : The correct nautical term for ropes used on a vessel, each with a specific name based on its use.
Liner : Originally a term for major warships in a battle line; now refers to large, prestigious passenger vessels.
List : The lean or tilt of a vessel to one side due to uneven weight distribution.
Loaded to the Gunwales : Having cargo loaded up to the ship’s rail; colloquially, being extremely drunk.
Loggerhead : An iron tool for driving caulking into seams; historically, also used in fights.
Log : A device for measuring a ship’s speed; also, a record of a ship’s activities.
Logbook : An official record of a ship’s voyage, including navigation details, weather, and other significant events.
Longitude : The angular distance east or west from the Prime Meridian, measured in degrees.
Lookout : A person assigned to watch for dangers or other ships.
Loose Cannon : An unsecured cannon rolling on deck, posing danger; colloquially, an unpredictable or uncontrollable person.
Lubber’s Hole : An opening in the platform at a mast’s top, allowing easy access without climbing the rigging.
Lubber’s Knot : A simple knot or one used by inexperienced sailors; also called a “granny knot”.
Lubber’s Line : A line inside a compass case indicating the ship’s heading.
Luff : The forward edge of a sail; ‘to luff up’ means turning the boat’s head into the wind.
Luffing : The condition when a sail is not fully filled with wind, often indicated by flapping.
Lying Ahull : A storm tactic where all sails are doused and the boat is left to drift.
MCA (Maritime and Coastguard Agency) : The organization responsible for maritime safety and regulation in the United Kingdom.
MHWS (Mean High Water Springs) : The average highest tidal height at spring tides.
MHWN (Mean High Water Neaps) : The average highest tidal height at neap tides.
MLWS (Mean Low Water Springs) : The average lowest tidal height at spring tides.
MLWN (Mean Low Water Neaps) : The average lowest tidal height at neap tides.
MMSI (Maritime Mobile Service Identity) : A unique identification number for maritime communications.
MV (Motor Vessel) : A prefix for a ship powered by engines, indicating it is a motor-driven vessel.
Magnetic Compass : A navigational instrument using a magnetized needle to indicate magnetic north.
Magnetic Deviation : The error of a compass reading due to magnetic influences on the vessel.
Magnetron : A high-powered vacuum tube used in radar systems aboard ships.
Mainbrace : The brace attached to the mainmast, essential for controlling the main yard.
Mainmast (or Main) : The tallest mast on a ship, supporting the primary sails.
Mainsheet : A line used to control the angle and shape of the mainsail, affecting sail trim and boom position.
Man Overboard! : A cry indicating that a person has fallen off the ship, initiating rescue procedures.
Man of War : A warship from the age of sail, heavily armed and used for combat.
Manifest : A detailed list of a ship’s cargo, passengers, and crew for the use of customs and other officials.
Marina : A facility for docking small ships and yachts, often with amenities like fuel, water, and electricity.
Marine Insurance : Insurance covering the loss or damage of ships, cargo, terminals, and any transport or cargo by which property is transferred.
Marine Salvage : The process of recovering a ship and its cargo after a shipwreck or other maritime casualty.
Mariner : A sailor or seaman experienced in seafaring.
Marines Soldiers Afloat : Royal Marines with duties including guarding ship’s officers; formed in 1664.
Marinized Engine : An automotive engine adapted for use in marine environments, resistant to corrosion and designed for cooling with seawater.
Maritime Administration : A governmental body responsible for maritime affairs, including regulation and promotion of the maritime industry.
Maritime Buoyage System : A system of buoys and markers used to aid navigation at sea, indicating channels, hazards, and other navigational information.
Maritime Domain Awareness : The understanding of anything associated with the maritime domain that could impact security, safety, economy, or environment.
Maritime Law : A body of laws, conventions, and treaties that govern private maritime business and other nautical matters, such as shipping or offenses occurring on open water.
Maritime Pilot : A navigator who guides ships through dangerous or congested waters, such as harbors or river mouths.
Maritime Safety : Measures and regulations to ensure safety at sea, including ship construction standards, equipment, and crew training.
Maritime Security : Protection against threats to the maritime domain, such as piracy, smuggling, or terrorism.
Marlinspike : A pointed iron hand tool used to separate strands of rope or wire cable for splicing.
Marconi Rig : A type of sail rigging with triangular sails attached to a mast, resembling a radio antenna; commonly seen on modern sailboats.
Mast : A vertical pole on a ship supporting sails and rigging; integral to a sailing vessel’s structure.
Mast Step : The socket or base in the keel where the mast is fixed, providing support and alignment.
Masthead : The top of a mast; also, a platform partway up the mast used for lookout and accessing the rigging.
Master : The commander of a commercial vessel in a shipboard organization or a senior naval officer responsible for seamanship and navigation.
Master-at-Arms : A naval non-commissioned officer in charge of discipline and law enforcement aboard a ship.
Mate : An officer on a merchant ship ranking below the master; responsible for the safety and security of the ship and crew.
Matelot : A traditional Royal Navy term for an ordinary sailor; derived from the French word for sailor.
Mayday : An international distress signal used by ships and aircraft in voice procedure radio communications to signal life-threatening emergencies.
Measured Mile : A nautical mile measured for testing a ship’s speed, typically marked by two pairs of navigational aids ashore.
Mercator Projection : A cylindrical map projection introduced by Gerardus Mercator in 1569, widely used in maritime navigation because it represents lines of constant true bearing as straight lines.
Meridian : An imaginary line on Earth passing through the poles, used in navigation to measure longitude.
Mess : An area on a ship where the crew eats; also refers to the group of crew members who eat together.
Mess Deck Catering : A system where a mess group collectively manages and prepares meals, common in naval ships.
Midshipman : A junior officer in naval training, often a cadet or officer candidate.
Mizzen : The shorter after-mast on a ketch or yawl; also, the sail on this mast.
Mizzen Staysail : A light sail set on a ketch or yawl, used in moderate conditions to improve downwind performance.
Mizzenmast (or Mizzen) : The third mast on a ship, typically on larger vessels, located aft of the mainmast.
Monkey Fist : A weighted ball woven from line, used for throwing a line to another location, such as from ship to dock.
Moor : To secure a boat to a mooring point or dock using lines or anchors.
Mooring : Securing a boat to a fixed point like a buoy or dock; also refers to the equipment used.
Mooring Buoy : A floating device that boats can tie up to, which is connected to an anchor on the seabed.
Mooring Line : A rope or cable used to secure a ship to a mooring buoy or quay.
Motorboat : A boat propelled by an internal combustion engine, used for recreation, transportation, or commercial purposes.
Mutiny : An open rebellion against the proper authorities, especially by sailors against their officers.
Muster : The assembly of crew or passengers for purposes of accounting and briefing, often conducted during drills or emergencies.
Muster Station : A designated area where passengers and crew assemble in case of an emergency for accountability and instructions.
Naval Architecture : The art and science of designing ships and other floating vessels.
Navigation : The process of monitoring and controlling the movement of a vessel from one place to another.
Navigation Lights : Lights displayed by a vessel at night or in poor visibility to indicate its position, heading, and status to other vessels.
Navigation Rules : Guidelines, also known as “rules of the road,” for avoiding collisions at sea and determining responsibility in the event of a collision.
Nautical Almanac : A publication containing astronomical data for marine navigation, including the positions of celestial bodies.
Nautical Chart : A graphic representation of maritime areas and adjacent coastal regions, used for navigation.
Nautical Dawn : The time in the morning when the sun is 12 degrees below the horizon, marking the beginning of nautical twilight.
Nautical Dusk : The time in the evening when the sun is 12 degrees below the horizon, marking the end of nautical twilight.
Nautical Mile : A unit of distance in marine navigation, approximately equal to 1.852 kilometers or 1.15078 statute miles.
Nautical Twilight : The period before sunrise and after sunset when the sun is between 6 and 12 degrees below the horizon; sufficient light for sailors to navigate using the horizon.
Neap Tide : A tide occurring just after the first or third quarters of the moon, when there is the least difference between high and low water levels.
Neptune : The Roman god of the sea; often referenced in maritime traditions and ceremonies.
Net Tonnage : A measure of a ship’s cargo-carrying capacity, calculated by deducting non-revenue-earning spaces from the gross tonnage.
Night Orders : Instructions left by the captain for officers on watch during the night.
Nipper : A short rope used to bind an anchor cable to a messenger line during anchoring operations, facilitating the cable’s movement.
No Room to Swing a Cat : A phrase indicating a lack of space, historically referring to cramped conditions on a ship where there wasn’t enough room to swing the ‘cat o’ nine tails’ whip.
Nun Buoy : A type of navigational buoy that is conical in shape and marks the starboard (right) side of a channel when returning from sea.
Oar : A long pole with a flat blade, used manually for rowing a boat.
Offing : The part of the sea visible from shore but beyond anchoring ground; sailing in the offing means sailing at a distance from the coast.
Oilskin : Waterproof clothing worn by sailors in foul weather to protect against rain and sea spray.
Old Man : A colloquial term for the captain of a vessel.
On the Rocks : A ship that has run aground on a rocky shoreline.
On the Wind : Sailing as close to the wind direction as possible; also known as close-hauled.
Ordinary Seaman : A sailor of the lowest rank in the deck crew, responsible for basic seamanship tasks.
Orderbook : A record or list detailing the orders placed with shipyards for the construction of new ships. This term is commonly used in the maritime industry to gauge the level of activity and demand in the shipbuilding sector. Related article: What is a Ship Order Book? A Clear Explanation for Traders and Investors.
Oreboat : A vessel, typically found on the Great Lakes, used primarily for transporting iron ore.
Orlop Deck : The lowest deck in a ship, especially in ships of the line, often covering the hold and used for storing cables and other equipment.
Outboard Motor : A detachable engine mounted on the stern of a boat, used for propulsion.
Outfall : The outlet of a drain or sewer into a body of water; in maritime terms, it can refer to the discharge point of a river or waste system into the sea.
Outhaul : A rope used to control the shape of a sail, particularly the foot, by pulling the clew outward along the boom.
Outward Bound : Departing from a port or harbor, heading towards the open sea.
Overall Length (LOA) : The total length of a boat or ship, measured from the foremost part of the bow to the aftermost part of the stern, excluding attachments like bowsprits. Related article: What Do Boat Measurements Mean? 11 Terms Explained! .
Overbear : Sailing downwind directly at another ship to steal or disrupt its wind.
Overboard : Over the side of the ship; in the water. A term used when something or someone falls off a vessel.
Overfall : Dangerous sea conditions with steep and breaking waves, often caused by opposing currents and winds in shallow areas.
Overhaul : The action of hauling buntline ropes over sails to prevent chafing; also, to examine and repair machinery thoroughly.
Overhead : The ceiling on a boat, technically the underside of the deck above.
Overreach : In sailing, maintaining a tack course too long, causing the vessel to sail beyond its optimal turning point.
Over the Barrel : A phrase referring to the practice of flogging sailors over a cannon’s barrel; colloquially means being in a helpless or difficult situation.
Overwhelmed : A term for a boat that has been overpowered by wind or waves, causing it to capsize or sink.
Owner : A traditional Royal Navy term for the captain, originating from the days when ships were often owned by their captains.
Ox-Eye : A cloud or weather phenomenon signaling the potential onset of a storm; a small, dark cloud that can foretell worsening weather conditions.
Packet Boat : A vessel that carries mail, cargo, and passengers on a regular schedule between ports.
Painter : The bow line used to tow or secure a dinghy or tender.
Panpan : An urgency call over the radio, requesting assistance but not indicating immediate danger.
Parbuckle : A method of lifting or lowering a cylindrical object using a doubled rope wrapped around it.
Parrel : A movable loop or collar securing the yard or gaff to the mast on a sailing vessel.
Part Brass Rags : An expression meaning to fall out with a friend; originates from the practice of sailors sharing cleaning materials (brass rags).
Passerelle : A gangway or boarding ramp used to access a vessel from a dock or another ship.
Pay : The action of filling a seam with pitch or caulking to prevent leaks; also refers to lubricating rigging or ropes.
Pay Off : To discharge a ship’s crew and settle accounts when a voyage is completed; also, when a ship’s bow falls away from the wind.
Paymaster : A naval officer responsible for financial matters, including paying and provisioning the crew.
Peak : The upper corner of a four-sided sail; also refers to the highest point of something.
Pier : A structure built out into the water for use as a landing place, promenade, or to protect or form a harbor.
Pier-head Jump : A last-minute assignment of a sailor to a warship just before its departure.
Pilot : A navigator or person qualified to steer ships through challenging waters, such as harbors or river mouths.
Pilot Boat : A vessel used to transport maritime pilots between land and the inbound or outbound ships they are piloting.
Pilot Ladder : A flexible ladder made of ropes and wooden steps, used for boarding and disembarking from ships.
Pilothouse : An enclosed space on a boat from where it is navigated and controlled; also known as the wheelhouse.
Pilotage : The act of navigating a ship through difficult or congested waters by a qualified pilot.
Pirate : A person who attacks and robs ships at sea without legal authority.
Pipe (Bos’n’s Call) : A whistle used by boatswains to issue commands on a ship through specific sounds or “pipes.”
Pipe Down : A signal indicating the end of the day, requiring silence and lights out; also means to stop talking.
Piping the Side : A ceremonial salute using the bosun’s pipe to honor important individuals boarding or leaving the ship.
Pitch : The up-and-down motion of a vessel’s bow and stern, rotating around its lateral axis. Read more about propeller pitch .
Pitching : The longitudinal rotation of a vessel about its beam axis, causing the bow and stern to move up and down.
Pitchpole : To capsize a boat end over end, rather than by rolling over sideways.
Plank Owner : An individual who was a member of the crew when a ship was commissioned.
Planing : When a boat is moving fast enough to be supported by hydrodynamic lift rather than buoyancy, allowing it to skim over the water.
Plimsoll Line : A marking on a ship’s side showing the legal limit to which it can be loaded, named after Samuel Plimsoll.
Points of Sail : The various angles of a sailing vessel in relation to the wind direction, such as close-hauled, beam reach, and running.
Pontoon : A flat-bottomed vessel or floating structure, often used to support bridges, docks, or for boarding purposes.
Poop Deck : A high deck on the aft (rear) of a ship’s superstructure. Read more about what is a poop deck on ships .
Pooped : Being swamped by a high, following sea washing over the stern; colloquially, being extremely tired or exhausted.
Port : The left-hand side of a ship when facing forward; marked with a red light at night.
Port Authority : An organization responsible for managing a port’s operations, including shipping, security, and infrastructure.
Port Bow : The forward left side of a ship when facing forward.
Port Hole : A circular window in a ship’s side, allowing light and air into the interior spaces.
Portlight : A window in the side of a ship or boat, which can usually be opened for ventilation.
Port of Call : A port where a ship stops during its voyage for supplies, repairs, or to load and unload cargo or passengers.
Port Quarter : The rear left side of a ship when facing forward.
Port Side : The left-hand side of a ship when facing forward.
Port Tack : When a sailing boat has the wind coming from the port side and the mainsail is on the starboard side.
Port Watch : The group of crew members assigned to duties during certain hours, traditionally on the port side.
Position Line (Line of Position) : A line on a chart indicating a boat’s possible location, derived from bearings, celestial observations, or other navigational data.
Press Gang : Groups used historically by navies, notably the Royal Navy, to forcibly recruit men into naval service.
Preventer (Gybe or Jibe Preventer) : A line used to prevent or control the boom during an accidental jibe, enhancing safety.
Privateer : A privately-owned vessel authorized by a government under a Letter of Marque to attack enemy ships during wartime.
Propeller : A mechanical device with blades that rotates to propel a ship forward by converting rotational energy into thrust.
Propeller Shaft : The shaft that connects the engine to the propeller, transmitting power for propulsion.
Propeller Walk (Prop Walk) : The tendency of a propeller to push the stern sideways due to its rotation, affecting maneuverability.
Prow : A poetic term for the bow of a ship. Read more about the prow of a ship .
Pulley : A wheel on an axle designed to support movement and change the direction of a taut cable or belt; used extensively in rigging.
Pulpit : A metal guardrail at the bow of a boat, providing safety for the crew working on the foredeck.
Pushpit : A metal guardrail at the stern of a boat, offering protection and a place to mount equipment.
Pusser : A naval term for the purser; the officer responsible for supplies and provisions on a ship.
Put About : To change the course of a ship by turning the bow into and through the wind; also known as tacking.
Pyrotechnics : Flares and fireworks used as distress signals or for celebrations and signaling.
Quadrant : A navigational instrument used historically for measuring angles up to 90 degrees, essential for celestial navigation before modern devices.
Quarantine : A period of isolation imposed on a ship arriving in port to prevent the spread of contagious disease; also, the area where such ships are held.
Quarter : The side of a boat between the stern and the beam, roughly midway along the boat’s length.
Quarterdeck : Traditionally, the aftermost deck of a warship, reserved for the ship’s officers; often near the stern and used for ceremonies and official functions.
Quartering Sea : Waves approaching a vessel from an angle on either quarter, which can cause rolling and pitching motions.
Quartermaster : A naval petty officer responsible for steering and signals; in merchant ships, a rating who steers the ship under the officer’s direction.
Quarters : Living accommodations on a ship; also refers to stations assigned to crew members for specific duties.
Quay (or Quayside) : A stone or metal platform lying alongside or projecting into water for loading and unloading ships.
Queen’s (King’s) Regulations : The comprehensive orders governing the Royal Navy of the UK, issued under the authority of the reigning monarch.
Quick Flashing Light : A navigational light that flashes at least 60 times per minute, used on buoys and lighthouses to aid in maritime navigation.
Raft : A flat structure made of buoyant materials or inflatable components, used for support or transportation over water; in maritime contexts, often used as a life-saving device.
Radar : Acronym for RAdio Detection And Ranging, an electronic system used for detecting and locating objects using radio waves.
Radar Beacon (Racon) : A radar transponder beacon that provides bearing and range information to ships by transmitting a coded signal when it receives a radar pulse.
Radar Reflector : A device that enhances a vessel’s visibility on radar screens by reflecting radar energy, making small boats more detectable.
Radio Direction Finder (RDF) : A device used to find the direction to a radio source, aiding in navigation by determining bearings.
Ram : The reinforced bow of a ship designed for ramming enemy vessels, historically used in naval warfare.
(1) In navigation, the alignment of two fixed points to guide a vessel.
(2) The difference between high and low tide levels.
(3) The distance at which a light or object is visible.
Range Finder : An instrument used to measure the distance from the observer to a target, important in navigation and gunnery.
Range Lights : Two lights aligned to form a navigational aid or mark a channel’s centerline, helping vessels maintain a safe course.
Ratlines : Rope ladders on a ship’s rigging, attached horizontally to shrouds, allowing the crew to climb the mast and access sails and yards.
Rating : An enlisted sailor in the Navy, classified according to their rank or job specialty.
Rations : The food allowance for sailors; historically, food supplies on a ship were carefully rationed during long voyages.
Reach : A sailing point approximately 60° to 160° off the wind, including close reach (60°–80°), beam reach (90°), and broad reach (120°–160°).
(1) To reduce a sail’s area in strong winds by folding or rolling part of it.
(2) A rock or coral formation shallow enough to ground a vessel.
Reef Knot : A simple binding knot used to join two ends of a rope together; also known as a square knot.
Reef Points : Cords attached to a sail for securing excess fabric after reefing, allowing the sail to be made smaller in strong winds.
Reef-Bands : Canvas strips sewn across sails for added strength at the reefing points.
Reef-Tackles : Ropes used in the operation of reefing sails, helping to gather and secure the reefed portion.
Reefing Pennant : A strong line used to pull down the sail’s cringle to the boom during reefing.
Reduced Cat : A lighter version of the cat o’ nine tails, historically used for disciplining boys on naval ships.
Red Duster : Traditional nickname for the British Civil Red Ensign, the flag flown by British merchant ships.
Register Ton : A unit of volume used in measuring a ship’s internal capacity, equivalent to 100 cubic feet.
Relative Bearing : The direction to an object relative to the ship’s heading, measured in degrees clockwise from the bow.
Righting Couple : The force that restores a ship to equilibrium after a heel, caused by the relationship between the center of buoyancy and the center of gravity.
Rig : The arrangement of masts, sails, and rigging on a vessel; different rig types include sloop, ketch, schooner, etc.
Rigging : The system of ropes, cables, or chains supporting a ship’s masts and controlling sails. More about Rigging !
Rigging Screw : A device used to adjust the tension of a ship’s standing rigging; also known as a turnbuckle.
Rigol : A rim or ‘eyebrow’ above a porthole or scuttle, designed to prevent water from entering.
Roach : The curved part of a sail’s leech (aft edge), extending beyond a straight line from head to clew, increasing sail area.
Roll : A vessel’s side-to-side motion, rotating about the fore-and-aft axis, caused by waves or wind.
Rolling Tackle : Pulleys and lines used to secure the yard to the weather side of the mast in rough seas, reducing rolling.
Rope’s End : A short length of rope used as a tool for summary punishment or as a general-purpose implement aboard ship.
Rudder : A flat piece, usually wood or metal, used to steer a ship by redirecting water flow. Read more about how a rudder functions on a ship .
Rudder Post : The vertical shaft connecting the rudder to the steering mechanism, allowing it to pivot.
Rudder Stock : The main shaft of the rudder, supporting it and transferring steering movements from the helm.
Rummage Sale : The sale of damaged or unclaimed cargo, derived from the French word ‘arrimage’ (loading of cargo).
Run : To sail with the wind directly behind the vessel, maximizing speed with sails set wing-on-wing.
Running Rigging : The movable rigging of a ship, including lines like sheets and halyards, used to control the position and shape of sails.
The Ropes : Refers to the lines used in a ship’s rigging; “knowing the ropes” means being familiar with the vessel’s operations.
Sagging : The condition of a ship when a wave trough is amidships, causing the middle part of the ship to bend downward.
Sail-plan : A set of drawings showing various sail combinations recommended for different conditions.
Sailing Certification : Official recognition of sailing competence by an established sailing educational body.
Saltie : A Great Lakes term for a vessel that also sails in ocean waters.
Sampson Post : A strong vertical post supporting a ship’s windlass and the heel of the bowsprit.
SAR (Search and Rescue) : Operations aimed at finding and helping vessels in distress.
SART (Search and Rescue Transponder) : A device used in search and rescue operations to locate vessels.
Scandalize : To temporarily reduce the area of a sail without properly reefing it, usually by raising the boom and reducing sail tension.
Scantling : A set of standard dimensions for parts of a structure or vessel, particularly in shipbuilding, ensuring structural integrity.
Scud : Low, fast-moving clouds observed mostly in squally weather.
Scudding : Being carried furiously along by a storm or strong wind.
Scuppers : Openings on the side rails that allow water to drain off the deck.
Scuttle : A small opening in a ship’s deck or hull; also, to deliberately sink a vessel.
Scuttlebutt : A barrel for drinking water on a ship; colloquially refers to gossip among sailors.
Sea Anchor : A device deployed in water to stabilize a vessel in heavy weather by increasing drag.
Sea Chest : An opening in a ship’s hull for water intake, used for cooling engines or ballast purposes.
Seacock : A valve that controls water intake or discharge through the hull.
Seafarer : A person who works aboard a sea-going ship; a sailor.
Seaman : A sailor or crew member, often referring to lower ranks.
Seaworthy : The condition of being fit and safe for navigating at sea.
Securité : A procedure word indicating a safety-related communication, less urgent than mayday or pan-pan.
Seelonce : A request for radio silence during a distress incident to ensure clear communication.
Self-Unloader : A Great Lakes term for a vessel equipped to unload its cargo without external equipment, using built-in conveyor systems.
Sennet Whip : A device made of braided rope used for summary punishment on ships.
Shackle : A metal link with a removable pin, used in various shapes for securing items like chains and ropes.
Sheave : A wheel or roller with a grooved rim in a block or pulley over which a rope runs.
Sheer : The upward curve of a ship’s deck line along its length, viewed from the side.
Sheet : A rope attached to the lower corner of a sail (the clew) for controlling its angle to the wind.
Ship : A large vessel capable of deep-water navigation; traditionally, a three-masted vessel square-rigged on all masts.
Ship’s Bell : A bell used for marking time aboard ship and regulating the crew’s watches.
Ship’s Company : The collective term for the officers and crew of a ship.
Shoal : Shallow water that presents a hazard to navigation; also, a sandbank or submerged ridge.
Shrouds : Part of the standing rigging, running from the mast to the sides of the ship for support.
Sick Bay : The medical compartment on a ship where sick or injured crew receive treatment.
Siren : A sound signal device using electricity or compressed air, used for warnings and signaling.
Skipper : The captain or master of a ship or boat, especially in smaller vessels.
Skysail : A very high sail, set above the royals, carried by only a few ships.
Skyscraper : A small, triangular sail set above the skysail in light winds to maximize sail area.
Slack Tide : The period when the tide is turning, and there is no horizontal flow of water.
Sloop : A single-masted sailing boat with one mainsail and one headsail (jib).
Slop Chest : A store aboard a ship selling items like clothing, tobacco, and toiletries to the crew.
Slush : Greasy substance from boiling or scraping fat in meat storage barrels, used for greasing rigging.
Slush Fund : Money obtained from selling ‘slush’, used for the crew’s benefit or unofficial purposes.
Small Bower (Anchor) : The smaller of two anchors carried at the bow of a ship.
Son of a Gun : Originally, a term for children born aboard ship; now used to refer affectionately to a person, sometimes with a hint of mischief.
Sonar : Sound Navigation And Ranging; a device for detecting objects underwater by emitting sound pulses and detecting echoes.
Sounding : Measuring the depth of water beneath a ship using a lead line or echo sounder.
Spar : A general term for poles like masts, booms, and yards used to support sails and rigging.
Spanker : A fore-and-aft sail set on the aft-most mast (the spanker mast) of a ship.
Spanker-Mast : The aft-most mast on vessels like schooners and barquentines, supporting the spanker sail.
Spindrift : Spray blown from wave crests by strong winds, often seen during storms.
Spinnaker : A large, balloon-like sail used for downwind sailing to maximize speed and performance.
Splice : To join two ropes or wire ends together by intertwining their strands, creating a strong union.
Spotlight : A powerful light used to illuminate areas or signals at night, aiding in navigation or search efforts.
Squall : A sudden, sharp increase in wind speed lasting minutes, often accompanied by rain or snow.
Stability : The ability of a ship to return to an upright position after being heeled by wind or waves.
Standing Rigging : The fixed lines, wires, or rods that support the ship’s masts and bowsprit.
Starboard : The right-hand side of a ship when facing forward; marked with a green light at night.
Starboard Tack : When a sailing boat has the wind coming from the starboard side and the mainsail is on the port side.
Station Keeping : Maintaining a vessel’s position relative to another vessel or fixed point, often used during operations like refueling at sea.
Stem : The very front part of the bow, running from the keel upwards; the forward-most part of the hull.
Stern : The rear or aft-most part of a ship.
Sternway : The backward movement of a ship through the water; opposite of headway.
Stevedore : A person employed at a dock to load and unload ships; also known as a longshoreman.
Stow : To pack or store items neatly and securely aboard a ship.
Stowaway : A person who hides aboard a ship to obtain free passage without paying.
Superstructure : The parts of a ship above the main deck, including cabins, bridge, and other structures.
Surge : A vessel’s temporary increase in speed or movement forward due to wave action or engine thrust.
Swab : A mop used for cleaning decks; also, a slang term for a sailor.
Swamp : To fill with water, but not sink; a condition where a boat is flooded.
Swell : Long-wave motion of the sea caused by distant wind or storms, often without immediate wind.
Swim Platform : A platform at the stern of a boat, close to the waterline, used for swimming or boarding.
Tabernacle : A hinged mast step that allows a mast to be lowered easily for passing under bridges or for maintenance.
Tack (noun) : The lower forward corner of a sail.
Tack (verb) : A maneuver where the boat turns its bow through the wind to change direction from one side to the other.
Tacking : Sailing close-hauled on alternate courses so that the wind shifts from one side of the boat to the other, achieved by repeatedly tacking.
Taffrail : The rail around the stern (back) of a ship, often ornate in older vessels.
Tailshaft : A metallic shaft connecting the propeller to the power engine, aiding in propulsion.
Taking the Wind Out of His Sails : Sailing in a way that steals the wind from another ship’s sails, causing it to slow down.
Tally : The action of hauling aft the sheets towards the ship’s stern.
Tang : A metal fitting for attaching rigging to a mast or spar.
Tank Top : The plating covering the double bottom in a ship’s hull, forming the bottom of cargo holds.
Tarpaulin : A protective covering made of canvas or other material, coated with tar, used to protect equipment from weather.
Teazer : A rope used as a punitive device aboard ships.
Tender : A small boat used to ferry people and supplies between a larger vessel and the shore.
Three Sheets to the Wind : A term describing a drunken sailor; metaphorically, a ship with its sheets (lines controlling the sails) loose, causing it to drift aimlessly.
Thwart : A transverse seat in a rowboat, used by a rower.
Tide : The periodic rise and fall of the ocean’s surface due to gravitational forces, mainly from the moon and sun.
Tide Tables : Published tables showing predicted times and heights of tides for specific locations, essential for navigation.
Tidal Stream : The horizontal movement of water due to tides, important in navigation for understanding currents.
Timoneer : A steersman of a ship, especially during specific maneuvers or in historical contexts.
Tiller : A lever attached to the rudder, used for steering a boat.
Tillerman : A person who steers a boat using a tiller.
Toe Rail : A low strip running around the edge of a boat’s deck for safety and structural integrity.
Toe the Line/Mark : To stand in line with toes aligned with a seam on the deck, used in naval parades; also means to conform strictly to rules or orders.
Togey : Another term for a rope used as a punitive device on ships.
Topgallant : The mast or sails above the topsails, the third tier in a square-rigged ship.
Topmast : The second section of a mast above the deck, carrying the topsails.
Topping Lift : A line used to support the boom of a sailboat when the sail is not raised, preventing it from dropping onto the deck.
Topsail : The second sail up a mast, either square or fore-and-aft; in square-rigged ships, the sail set above the course sail.
Topsides : The part of a ship’s hull above the waterline; also refers to above-deck areas.
Touch and Go : A situation where the ship’s bottom grazes the seafloor but doesn’t become grounded, allowing it to continue sailing.
Towing : The process of pulling a vessel through the water by means of lines or cables.
(1) The actual path over the ground that a boat follows.
(2) A fitting on the mast or boom for a sail’s slide.
(3) A fitting for a traveller, allowing movement along a fixed path.
TrackLink : A GPS tracking app for student logbooks in sailing education.
Traffic Separation Scheme : Designated shipping corridors that separate incoming and outgoing vessels to reduce the risk of collision.
Trapeze : A harness used by crew members to balance a sailing dinghy by allowing them to lean out over the side, counteracting heel.
Transom : The flat surface forming the stern of a boat. Read more: What Is a Transom on a Boat? A Beginner’s Guide .
Travellers : Fittings that slide on a rod or line, commonly used for adjusting the position of the mainsheet or other control lines.
(1) Adjusting the sails for optimal performance.
(2) Adjusting the boat’s load or angle for optimal fore-and-aft balance.
Trim Tab : A small control surface attached to a larger control surface, like a rudder or aileron, used to maintain a desired position or reduce steering effort.
Trimaran : A boat with a main hull and two smaller outrigger hulls for stability and speed.
Trip Line : A line attached to the crown of an anchor to help retrieve it by pulling it out backwards if it becomes stuck.
True Wind : The actual speed and direction of the wind felt when stationary, as opposed to apparent wind experienced when moving.
Truck : A wooden cap at the top of a mast, often with holes for signal halyards.
Trunnel : A wooden peg or dowel used in traditional shipbuilding to fasten timbers together; also known as a treenail.
Tsunami : A long, high sea wave caused by an earthquake or other disturbance, potentially dangerous for ships near the coast.
Turnbuckle : A device used to adjust the tension or length of rigging, cables, or ropes by turning a central threaded body.
Turn To : An order to begin work or resume duties on a ship.
Twin Screw : A ship with two propellers, one on each side of the keel, providing improved maneuverability and redundancy.
Turtling : A capsizing incident where a sailboat overturns completely, with the mast pointing down and the hull resembling a turtle shell.
Unbend : To remove a sail from its yard or stay; to untie or detach.
Under the Weather : Serving a watch on the weather side of the ship, exposed to wind and spray, often leading to feeling ill.
(1) In a general sense, a vessel that is moving or navigating, not anchored, moored, or aground.
(2) Specifically, a boat is underway when it is not fastened to the shore, at anchor, or aground.
Underwater Hull (or Underwater Ship) : The section of a vessel that is submerged in water, typically visible only when the vessel is in drydock.
Unfurl : To spread out or open a sail so that it catches the wind.
Unship : To remove something from its proper place on a ship, such as unshipping the oars.
Up Haul : A line used to raise equipment vertically, such as the spinnaker pole on a sailboat.
Upper Deck : The highest continuous deck on a ship, running the full length.
Upper-yardmen : Sailors selected for advanced training or development, often earmarked for higher office or specialized duties.
V-berth : A bed or sleeping space located at the bow of a boat, typically in a V-shape.
Vanishing Angle : The critical angle of heel beyond which a vessel cannot right itself and risks capsizing.
Vang (or Kicking Strap) : A line or rigging used to control the angle of the sailboat’s boom relative to the wind.
(1) A clockwise shift in the wind’s direction.
(2) To gradually and controlledly pay out an anchor cable or rope.
Vessel : A general term for any ship or boat.
VHF (Very High Frequency) : A radio frequency range used for marine communication, typically between 156 and 174 MHz.
Visor : The bow door of a roll-on/roll-off (RoRo) ferry, which opens to allow vehicles to drive on and off.
VMG (Velocity Made Good) : A measure of the speed at which a vessel is moving toward its destination, considering both its course and the current.
Voyage : A journey by sea from one port to another.
Wales : Thick, strong planks running lengthwise along the lower part of a ship’s side, contributing to structural integrity.
Wake : The trail of disturbed water left behind a boat as it moves through the water.
Wardroom : The living quarters or mess area for commissioned officers on a warship.
Watch : A designated period during which part of the crew is on duty, with changes marked by the ship’s bell.
Watercraft : General term for all types of water transport vessels, including ships, boats, and personal watercraft.
Waterline : The line where the hull of a ship meets the surface of the water.
Watertight : Sealed to prevent water ingress, essential for a ship’s compartments to maintain buoyancy.
Way : Movement of a ship through the water; making way means the ship is moving.
Weather Deck : The deck of a ship that is exposed to the weather, usually the main or upper deck.
Weather Gage : A favorable position relative to another vessel concerning the wind, giving a tactical advantage.
Weather Helm : The tendency of a boat to turn into the wind, requiring the tiller or wheel to be pulled windward for straight-line sailing.
Weather Side : The side of a ship that is exposed to the wind.
Weatherly : Describes a ship that sails well into the wind with minimal leeway.
Weigh Anchor : The action of lifting the anchor in preparation for sailing.
Wells : Sections in the ship’s hold designated for pumps or for containing liquids.
Wheelhouse : The area of a ship where the steering wheel is located; often synonymous with pilothouse or bridge.
Wheel : The steering apparatus of a ship, connected to the rudder.
Whisker Pole : A lightweight pole used to extend the clew of a headsail, especially when running downwind.
White Horses : Waves with foam or spray on their tops, typically formed in strong winds.
Wide Berth : Allowing ample space between two moored ships for maneuvering; also means to avoid something by a large margin.
Wiggle Room : Nautical slang for the extra space or flexibility needed in navigation or maneuvering.
WGS84 (World Geodetic System 1984) : The most common chart datum used in global positioning systems.
Winch : A mechanical device with a drum and handle, used to haul or adjust tension on ropes or cables, aiding in sail control.
Windage : The resistance of a boat to the wind, caused by parts like rigging, spars, and crew.
Windbound : Being confined to a particular area due to contrary winds preventing departure.
Windlass : A mechanical device, often horizontal, used for hauling anchor chains or ropes, providing greater mechanical advantage than block and tackle.
Windward : The direction from which the wind blows; opposite of leeward.
Wavelength : The distance between successive crests of waves, including radio waves and sea waves.
X-Band : A frequency band used in radar systems, specifically in the 7.0 to 11.2 GHz range, often used in marine radars for navigation and collision avoidance.
Xebec : A small, fast, three-masted Mediterranean sailing ship, used from the 16th to 19th centuries.
XTE (Cross Track Error) : The perpendicular distance a vessel has deviated from its planned track or course between two waypoints. It is a key parameter in navigation to ensure a vessel follows its intended route.
Yacht : A recreational boat or ship used for pleasure cruising or racing.
Yankee : A type of jib, a high-clewed headsail typically used on sailboats for performance.
Yard : A horizontal spar from which a square sail is suspended on a sailing ship.
Yardarm : The outer extremities of a yard. Commonly referenced in phrases like “hanging from the yardarm” or “sun over the yardarm.”
Yarr : A traditional acknowledgment of an order or agreement among sailors; often used in popular culture as “Arrr.”
Yaw : The motion of a vessel rotating about its vertical axis, causing the bow to swing from side to side.
Yawl : A two-masted sailing vessel with the mizzen mast positioned aft of the rudder post.
Zephyr : A gentle, light breeze; often used in nautical contexts to describe mild winds that are favorable for sailing.
Zincs : Sacrificial anodes typically made of zinc, mounted on a boat’s hull to prevent galvanic corrosion by corroding themselves instead of the more important metal parts of the boat.
Zulu : A type of Scottish fishing boat used in the 19th century, characterized by a straight stem and a steeply raked stern.
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