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Nautical Terms

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This Nautical Terms Glossary will help you understand the basic terminology used in the boating and marine industry.  The listing is quite comprehensive but is in no way considered complete or finalized.  If you come across a nautical term that is not listed, please drop us an email so we can incorporate the information into our glossary.


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ABAFT - Toward the rear (stern) of the boat. Behind.

ABEAM - At right angles to the keel of the boat, but not on the boat.

ABOARD - On or within the boat.

ABOVE DECK - On the deck (not over it - see ALOFT)

ABREAST - Side by side; by the side of.

ADRIFT - Loose, not on moorings or towline.

AFT - Toward the stern of the boat.

AGROUND - Touching or fast to the bottom.

AHEAD - In a forward direction.

AIDS TO NAVIGATION - Artificial objects to supplement natural landmarks indicating safe and unsafe waters.

ALEE - Away from the direction of the wind. Opposite of windward.

ALOFT - Above the deck of the boat.

AMIDSHIPS - In or toward the center of the boat.

ANCHOR – A heavy metal device, fastened to a chain or line, to hold a vessel in position, partly because of its weight, but chiefly because the designed shape digs into the bottom.

ANCHORAGE - A place suitable for anchoring in relation to the wind, seas and bottom.

ASTERN - In back of the boat, opposite of ahead.

ATHWARTSHIPS - At right angles to the centerline of the boat; rowboat seats are generally athwart ships.

AWEIGH - The position of anchor as it is raised clear of the bottom.


BATTEN DOWN - Secure hatches and loose objects both within the hull and on deck.

BEACON - A lighted or unlighted fixed aid to navigation attached directly to the earth's surface. (Lights and daybeacons both constitute "beacons.")

BEAM - The greatest width of the boat.

BEARING - The direction of an object expressed either as a true bearing as shown on the chart, or as a bearing relative to the heading of the boat.

BELOW - Beneath the deck.

BIGHT - The part of the rope or line, between the end and the standing part, on which a knot is formed. BILGE - The interior of the hull below the floor boards.

BILGE - The interior of the hull below

BITTER END - The last part of a rope or chain.The inboard end of the anchor rode.

BLOCK- A wooden or metal case enclosing one or more pulleys and having a hook, eye, or strap by which it may be attached.

BOAT - A fairly indefinite term. A waterborne vehicle smaller than a ship. One definition is a small craft carried aboard a ship.

BOAT HOOK - A short shaft with a fitting at one end shaped to facilitate use in putting a line over a piling, recovering an object dropped overboard, or in pushing or fending off.

BOOT TOP - A painted line that indicates the designed waterline.

BOW - The forward part of a boat.

BOW LINE - A docking line leading from the bow.

BOW SPRING LINE - A bow pivot line used in docking and undocking, or to prevent the boat from moving forward or astern while made fast to a pier.

BOWLINE KNOT - A knot used to form a temporary loop in the end of a line.

BOWSPRIT - A spar extending forward from the bow.

BRIDGE - The location from which a vessel is steered and its speed controlled. "Control Station" is really a more appropriate term for small craft.

BRIDLE - A line or wire secured at both ends in order to distribute a strain between two points.

BRIGHTWORK - Varnished woodwork and/or polished metal.

BROW - The device used to allow passage of personnel between the shore and a ship.  See also gangplank or gangway.

BULKHEAD - A vertical partition separating compartments.

BULWARK – A raised portion of the deck designed to serve as a barrier.

BUOY - An anchored float used for marking a position on the water or a hazard or a shoal and for mooring.

BURDENED VESSEL - That vessel which, according to the applicable Navigation Rules, must give way to the privileged vessel. The term has been superseded by the term "give-way".


CABIN - A compartment for passengers or crew.

CAPSIZE - To turn over.

CAST OFF - To let go.

CATAMARAN - A twin-hulled boat, with hulls side by side.

CHAFING GEAR - Tubing or cloth wrapping used to protect a line from chafing on a rough surface.

CHANNEL - 1. That part of a body of water deep enough for navigation through an area otherwise not suitable. It is usually marked by a single or double line of buoys and sometimes by range markers. 2. The deepest part of a stream, bay, or strait, through which the main current flows. 3. A name given to a large strait, for example, the English Channel.

CHART - A map for use by navigators.

CHINE - The intersection of the bottom and sides of a flat or v-bottomed boat.

CHOCK - A fitting through which anchor or mooring lines are led. Usually U-shaped to reduce chafe.

CID – Referring to the cubic inch displacement of an engine, e.g., 454-cid gas engine.

CLEAT - A fitting to which lines are made fast. The classic cleat to which lines are belayed is approximately anvil-shaped.

CLOVE HITCH - A knot for temporarily fastening a line to a spar or piling.

COAMING - A vertical piece around the edge of a cockpit, hatch, etc. to prevent water on deck from running below.

COCKPIT - An opening in the deck from which the boat is handled.

COIL - To lay a line down in circular turns.

COMPASS - Navigation instrument, either magnetic (showing magnetic north) or gyro (showing true north).

COMPASS CARD - Part of a compass, the card is graduated in degrees, to conform with the magnetic meridian-referenced direction system inscribed with direction which remains constant; the vessel turns, not the card.

COMPASS ROSE - The resulting figure when the complete 360° directional system is developed as a circle with each degree graduated upon it, and with the 000° indicated as True North. True North is also known as true rose. This is printed on nautical charts for determining direction.

COURSE - The direction in which a boat is steered.

CUDDY - A small shelter cabin in a boat.

CURRENT - The horizontal movement of water.


DAYBEACON - A fixed navigation aid structure used in shallow waters upon which is placed one or more daymarks.

DAYMARK - A signboard attached to a daybeacon to convey navigational information presenting one of several standard shapes (square, triangle, rectangle) and colors (red, green, orange, yellow, or black). Daymarks usually have reflective material indicating the shape, but may also be lighted.

DEAD AHEAD - Directly ahead.

DEAD ASTERN - Directly aft.

DEAD RECKONING - A plot of courses steered and distances traveled through the water.

DEADRISE – The angle from the bottom of the hull (not the keel) to the chine.

DECK - A permanent covering over a compartment, hull or any part thereof.

DEEP-V HULL – A hull designed to go through the water and not capable of planning speed.

DINGHY - A small open boat. A dinghy is often used as a tender for a larger craft.

DISPLACEMENT - The weight of water displaced by a floating vessel, thus, a boat's weight.

DISPLACEMENT HULL - A type of hull that plows through the water and is not capable of planning speed, displacing a weight of water equal to its own weight even when more power is added.

DOCK - A protected water area in which vessels are moored.The term is often used to denote a pier or a wharf.

DOLPHIN - A group of piles driven close together and bound with wire cables into a single structure.

DRAFT - The depth of water a boat draws.


EASE - To slacken or relieve tension on a line.

EBB - A receding current.

EBB TIDE - A receding tide.

EVEN KEEL - When a boat is floating on its designed waterline, it is said to be floating on an even keel.

EYE OF THE WIND - The direction from which the wind is blowing.

EYE SPLICE - A permanent loop spliced in the end of a line.


FAST - Said of an object that is secured to another.

FATHOM - Six feet.

FENDER - A cushion, placed between boats, or between a boat and a pier, to prevent damage.

FIGURE EIGHT KNOT - A knot in the form of a figure eight, placed in the end of a line to prevent the line from passing through a grommet or a block.

FLAME ARRESTER - A safety device, such as a metal mesh protector, to prevent an exhaust backfire from causing an explosion; operates by absorbing heat.

FLARE - The outward curve of a vessel's sides near the bow. A distress signal.

FLOOD - A incoming current.

FLOORBOARDS - The surface of the cockpit on which the crew stand.

FLUKE - The palm of an anchor.

FLYING BRIDGE - An added set of controls above the level of the normal control station for better visibility. Usually open, but may have a collapsible top for shade.

FOLLOWING SEA - An overtaking sea that comes from astern.

FORE-AND-AFT - In a line parallel to the keel.

FOREFOOT – The underwater shape of the hull at the bow.

FOREPEAK - A compartment in the bow of a small boat.

FORWARD - Toward the bow of the boat.

FOULED - Any piece of equipment that is jammed or entangled, or dirtied.

FOUNDER - when a vessel fills with water and sinks.

FREEBOARD - The minimum vertical distance from the surface of the water to the gunwale.


GAFF - A spar to support the head of a gaff sail.

GALLEY - The kitchen area of a boat.

GANGPLANK - A moveable bridge used in boarding or leaving a ship at a pier.

GANGWAY - The area of a ship's side where people board and disembark.

GEAR - A general term for ropes, blocks, tackle and other equipment.

GIVE-WAY VESSEL - A term used to describe the vessel which must yield in meeting, crossing, or overtaking situations.

GPH – Gallons per hour of fuel consumption.

GRAB RAILS - Hand-hold fittings mounted on cabin tops and sides for personal safety when moving around the boat.

GROUND TACKLE - A collective term for the anchor and its associated gear.

GUNNEL – The upper edge of the sheerline (also gunwale).

GUNWALE - The upper edge of a boat's sides (also gunnel).


HARBOR - A safe anchorage, protected from most storms; may be natural or man-made, with breakwaters and jetties; a place for docking and loading.

HARD CHINE - An abrupt intersection between the hull side and the hull bottom of a boat so constructed.

HATCH - An opening in a boat's deck fitted with a watertight cover.

HEAD - A marine toilet. Also the upper corner of a triangular sail.

HEADING - The direction in which a vessel's bow points at any given time.

HEADWAY - The forward motion of a boat. Opposite of sternway.

HEAVE TO - To bring a vessel up in a position where it will maintain little or no headway, usually with the bow into the wind or nearly so.

HEEL - To tip to one side.

HELM - The wheel or tiller controlling the rudder. HELMSPERSON - The person who steers the boat.

HITCH - A knot used to secure a rope to another object or to another rope, or to form a loop or a noose in a rope.

HOLD - A compartment below deck in a large vessel, used solely for carrying cargo.

HULL - The main body of a vessel.

HULL SPEED – The maximum practical speed of a displacement hull.  To calculate, take the square root of the LWL (waterline hull length) and multiply by 1.34.

HYPOTHERMIA - A life-threatening condition in which the body's warming mechanisms fail to maintain normal body temperature and the entire body cools.


INBOARD - More toward the center of a vessel; inside; a motor fitted inside a boat.

INTRACOASTAL WATERWAY - ICW: bays, rivers, and canals along the coasts (such as the Atlantic and Gulf of Mexico coasts), connected so that vessels may travel without going into the sea.


JACOBS LADDER - A rope ladder, lowered from the deck, as when pilots or passengers come aboard.

JETTY - A structure, usually masonry, projecting out from the shore; a jetty may protect a harbor entrance.


KEDGE - To use an anchor to move a boat by hauling on the anchor rode; a basic anchor type.

KEEL - The centerline of a boat running fore and aft; the backbone of a vessel.

KETCH - A two-masted sailboat with the smaller after mast stepped ahead of the rudder post.

KNOT - A measure of speed equal to one nautical mile (6076 feet) per hour. To convert knots to statute mph, multiply by 1.14.

KNOT - A fastening made by interweaving rope to form a stopper, to enclose or bind an object, to form a loop or a noose, to tie a small rope to an object, or to tie the ends of two small ropes together.


LATITUDE - The distance north or south of the equator measured and expressed in degrees.

LAZARETTE - A storage space in a boat's stern area.

LEE - The side sheltered from the wind.

LEEWARD - The direction away from the wind. Opposite of windward.

LEEWAY - The sideways movement of the boat caused by either wind or current.

LINE - Rope and cordage used aboard a vessel.

LOG - A record of courses or operation. Also, a device to measure speed.

LONGITUDE - The distance in degrees east or west of the meridian at Greenwich, England.

LUBBER'S LINE - A mark or permanent line on a compass indicating the direction forward parallel to the keel when properly installed.


MARLINSPIKE - A tool for opening the strands of a rope while splicing.

MAST - A spar set upright to support rigging and sails.

MIDSHIP - Approximately in the location equally distant from the bow and stern.

MODIFIED-V HULL – A planning hull form with generally less than 18 degrees of transom deadrise.

MONOHULL - A boat with one hull.

MOORING - An arrangement for securing a boat to a mooring buoy or a pier.

MOORING BUOY - A buoy secured to a permanent anchor sunk deeply into the bottom.


NAUTICAL MILE - One minute of latitude; A measurement used in salt water approximately 6,076 feet - about 1/8 longer than the statute mile of 5,280 feet.

NAVIGATION - The art and science of conducting a boat safely from one point to another.

NAVIGATION RULES - The regulations governing the movement of vessels in relation to each other, generally called steering and sailing rules.


OUTBOARD - Toward or beyond the boat's sides. A detachable engine mounted on a boat's stern.

OUTDRIVE - A propulsion system for boats with an inboard engine operating an exterior drive, with drive shaft, gears, and propeller; also called stern-drive and inboard/outboard.

OVERBOARD - Over the side or out of the boat.


PAINTER - A line attached to the bow of a boat for use in towing or making fast.

PASSARELLA - A retractable brow often installed on yachts.

PAY OUT - To ease out a line, or let it run in a controlled manner.

PENNANT (sometimes PENDANT) - The line by which a boat is made fast to a mooring buoy.

PERSONAL FLOTATION DEVICE (PFD) - PDF is official terminology for life jacket. When properly used, the PDF will support a person in the water. Available in several sizes and types.

PIER - A loading platform extending at an angle from the shore.

PILE - A wood, metal or concrete pole driven into the bottom. Craft may be made fast to a pile; it may be used to support a pier (see PILING) or a float.

PILING - Support, protection for wharves, piers etc.; constructed of piles (see PILE)

PILOTING - Navigation by use of visible references, the depth of the water, etc.

PITCH - 1. The alternate rise and fall of the bow of a vessel proceeding through waves; 2. The theoretical distance advanced by a propeller in one revolution; 3. Tar and resin used for caulking between the planks of a wooden vessel.

PITCHPOLING - A small boat being thrown end-over-end in very rough seas.

PLANING - A boat is said to be planing when it is essentially moving over the top of the water rather than through the water.

PLANING HULL - A type of hull shaped to glide easily across the water at high speed.

PLANING SPEED – The point at which an accelerating hull rises onto the top of the water.  To calculate a hull’s planing speed, multiply the square root of the waterline length by 2.

PORT - The left side of a boat looking forward. A harbor.

PRIVILEGED VESSEL - A vessel which, according to the applicable Navigation Rule, has right-of-way (this term has been superseded by the term "stand-on").

PROPELLER - A rotating device, with two or more blades, that acts as a screw in propelling a vessel.


QUARTER - The sides of a boat aft of amidships.

QUARTERING SEA - Sea coming on a boat's quarter.


REEF - To reduce the sail area.

RIGGING - The general term for all the lines of a vessel.

RODE - The anchor line and/or chain.

ROLL - The alternating motion of a boat, leaning alternately to port and starboard; the motion of a boat about its fore-and-aft axis.

ROPE - In general, cordage as it is purchased at the store. When it comes aboard a vessel and is put to use it becomes line.

RUDDER - A vertical plate or board for steering a boat.

RUN - To allow a line to feed freely.

RUNNING LIGHTS - Lights required to be shown on boats underway between sundown and sunup.


SATELLITE NAVIGATION - A form of position finding using radio transmissions from satellites with sophisticated on-board automatic equipment.

SCOPE - Technically, the ratio of length of anchor rode in use to the vertical distance from the bow of the vessel to the bottom of the water. Usually six to seven to one for calm weather and more scope in storm conditions.

SCREW - A boat's propeller.

SCUPPERS - Drain holes on deck, in the toe rail, or in bulwarks or (with drain pipes) in the deck itself.

SEA ANCHOR - Any device used to reduce a boat's drift before the wind.

SEA COCK - A through hull valve, a shut off on a plumbing or drain pipe between the vessel's interior and the sea.

SEA ROOM - A safe distance from the shore or other hazards.

SEAMANSHIP - All the arts and skills of boat handling, ranging from maintenence and repairs to piloting, sail handling, marlinespike work, and rigging.

SEAWORTHY - A boat or a boat's gear able to meet the usual sea conditions.

SECURE - To make fast.

SEMI-DISPLACEMENT HULL – A hull designed to operate economically at low speeds while still able to attain planning speed performance.

SET - Direction toward which the current is flowing.

SHACKLE - A "U" shaped connector with a pin or bolt across the open end.

SHEAR PIN - A safety device, used to fasten a propeller to its shaft; it breaks when the propeller hits a solid object, thus preventing further damage.

SHEERLINE – The fore-and-aft line along the top edge of the hull.

SHEET BEND - A knot used to join two ropes. Functionally different from a square knot in that it can be used between lines of different diameters.

SHIP - A larger vessel usually thought of as being used for ocean travel. A vessel able to carry a "boat" on board.

SHOAL - An offshore hazard to navigation at a depth of 16 fathoms (30 meters or 96 feet) or less, composed of unconsolidated material.

SLACK - Not fastened; loose. Also, to loosen.

SLOOP - A single masted vessel with working sails (main and jib) set fore and aft.

SOLE - Cabin or saloon floor. Timber extensions on the bottom of the rudder. Also the molded fiberglass deck of a cockpit.

SOUNDING - A measurement of the depth of water.

SPLICE - To permanently join two ropes by tucking their strands alternately over and under each other.

SPRING LINE - A pivot line used in docking, undocking, or to prevent the boat from moving forward or astern while made fast to a dock.

SQUALL - A sudden, violent wind often accompanied by rain.

SQUARE KNOT - A knot used to join two lines of similar size. Also called a reef knot.

STANDING PART - That part of a line which is made fast.The main part of a line as distinguished from the bight and the end.

STAND-ON VESSEL - That vessel which has right-of-way during a meeting, crossing, or overtaking situation.

STARBOARD - The right side of a boat when looking forward.

STATUTE MILE – Measurement used in fresh water. A stature mile equals 5,280 feet.

STEM - The forward most part of the bow.

STERN - The after part of the boat.

STERN LINE - A docking line leading from the stern.

STOP WATER - A soft wooden dowel that is inserted into a hole drilled athwart ship, inside the rabbit, (which is there to accept the front edge of planking), where the keel and stem are joined. The dowel swells when wet and prevents water from migrating into the hull through the joint created by the keel / stem connection and found in all wooden boats, if properly constructed.

STOW - To put an item in its proper place.

SWAMP - To fill with water, but not settle to the bottom.


TACKLE - A combination of blocks and line to increase mechanical advantage.

TENDER – Refers to a dinghy or a lack of stability.

THWART - A seat or brace running laterally across a boat.

THWARTSHIPS - At right angles to the centerline of the boat.

TIDE - The periodic rise and fall of water level in the oceans.

TILLER - A bar or handle for turning a boat's rudder or an outboard motor.

TOPSIDES - The sides of a vessel between the waterline and the deck; sometimes referring to onto or above the deck.

TRANSOM - The stern cross-section of a square sterned boat.

TRIM - Fore and aft balance of a boat.

TRIMARAN - A boat with three hulls.

TRIPLINE - A line fast to the crown of an anchor by means of which it can be hauled out when dug too deeply or fouled; a similar line used on a sea anchor to bring it aboard.

TRUE NORTH POLE - The north end of the earth's axis. Also called North Geographic Pole. The direction indicated by 000° (or 360°) on the true compass rose.

TRUE WIND - The actual direction from which the wind is blowing.

TURNBUCKLE - A threaded, adjustable rigging fitting, used for stays, lifelines and sometimes other rigging.


UNDERWAY - Vessel in motion, i.e., when not moored, at anchor, or aground.


V BOTTOM - A hull with the bottom section in the shape of a "V".

VARIATION - The angular difference between the magnetic meridian and the geographic meridian at a particular location.

VHF RADIO - A very high frequency electronic communications and direction finding system.


WAKE - Moving waves, track or path that a boat leaves behind it, when moving across the waters.

WATERLINE - A line painted on a hull which shows the point to which a boat sinks when it is properly trimmed (see BOOT TOP).

WAY - Movement of a vessel through the water such as headway, sternway or leeway.

WHARF - A man-made structure bonding the edge of a dock and built along or at an angle to the shoreline, used for loading, unloading, or tying up vessels.

WINCH - A device used to increase hauling power when raising or trimming sails.

WINDWARD - Toward the direction from which the wind is coming.



There are no boating terms under this heading.


YACHT - A pleasure vessel, a pleasure boat; in American usage the idea of size and luxury is conveyed, either sail or power.

YAW - To swing or steer off course, as when running with a quartering sea.

YAWL - A two-masted sailboat with the small mizzen mast stepped abaft the rudder post.



There are no boating terms under this heading.

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