"Dreams can't come true without first dreaming...there is no harvest without first sowing seed"
James J Steele

Nautical Terminology

Nautical Terminology


As a new pontoon boat owner, yet with years of being familiar with boats, I felt I needed to brush up on some common and uncommon nautical terminology…

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z


ABOARD – On or in the boat.
ADRIFT – Loose, not on moorings or towline
AFLOAT – On the water.
AFT – Toward the stern of the boat. The aft of a ship is towards the rear of the ship or the back of a boat.
AGROUND – Touching bottom.
AMIDSHIP – Center or middle of the boat.
AHEAD – In a forward direction.
ALEE – Away from the direction of the wind. Opposite of windward.
ANCHOR – (1) An iron casting shape to grip the lake bottom to hold the boat.( 2) The act of setting the anchor.
ANCHORAGE – A place suitable for dropping anchor in relation to the wind, seas, and bottom.
ASHORE – On the shore.
ASTERN – Toward the stern.
AUTOMATIC CHARGING RELAY (ACR) – An ACR parallels (combines) batteries during charging, and isolates them when charging has stopped and after the battery voltage has fallen. An ACR is intended to keep a load from discharging both of the batteries.
AUTOMATIC IDENTIFICATION SYSTEM (AIS) – An automatic tracking system used on ships and by vessel traffic services (VTS) for identifying and locating vessels by electronically exchanging data with other nearby ships, AIS base stations, and satellites.
AWEIGH – The position of the anchor as it is raised clear of the bottom.


BAIL – To remove water from the bottom of the boat with a pump, bucket, sponge, etc.
BAIT WELL – A miniature Live well used to store and keep live bait alive and healthy.
BATTEN DOWN – Secure hatches and loose objects both within the hull and on deck.
BEAM – The widest point on the boat.
BEARING – Relative position or direction of an object from the boat.
BIGHT – The part of the rope or line, between the end and the standing part, on which a knot is formed.
BILGE – The lowest interior section of the boat hull.
BILGE KEELS – The raised areas or aluminum extrusions on the bottom of a boat that parallel the keel.
BITTER END – The last part of a rope or chain. The inboard end of the anchor rode.
BOARDING – To enter the boat.
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.
BOUNDARY WATERS – A body of water between two areas of jurisdiction; i.e., a river between two states.
BOW – The front of the boat.
BOW LINE – A docking line leading from the bow.
BOWLINEA knot used to form a temporary loop at the end of a line.
BULKHEAD – Vertical partition (wall) in a boat.
BUOY – An anchored float marking the position on the water, a hazard, a shoal, and for mooring,
BUNKS – Carpeted trailer hull supports.
BURDENED VESSEL – Term for the boat that must “give way” to boats with the right-of-way.


CAPACITY PLATE – A plate that provides maximum weight capacity and engine horsepower rating information. It is located in full view of the helm.
CAPSIZE – To turn over.
CAST-OFF – To unfasten mooring lines in preparation for departure.
CENTERLINE – A lengthwise imaginary line that runs fore and aft with the boat’s keel.
CHART – A map used by navigators
CHINE – The point on a boat where the side intersects (meets) the bottom.
CHOCK – A fitting through which anchor or mooring lines are led. Usually, U-shaped to reduce chafe.
CLEAT – A deck fitting with ears to which lines are fastened.
CLOVE HITCHA knot for temporarily fastening a line to a spar or piling.
CONSOLE – Also called helm. The steering wheel area of the boat.
CONTROLLER AREA NETWORK (CANBUS) – A robust bus standard designed to allow micro-controllers and devices to communicate with each other in applications without a host computer.
COURSE – The direction in which a boat is steered.
CRANKING BATTERY – The main battery used for engine starting and electrical circuits.
CURRENT – Water moving in a horizontal direction.


DEAD AHEAD – Directly ahead.
DEAD ASTERN – Directly aft.
DECK – The open surface on the boat where the passengers walk.
DEEP-CYCLE BATTERIES – Special long-running batteries that can be repeatedly discharged and recharged without significant loss of power.
DIGITAL SELECTIVE CALLING (DSC) – A standard for sending pre-defined digital messages via medium frequency (MF), high frequency (HF), and very high frequency (VHF) maritime radio systems. It is a core part of the Global Maritime Distress and Safety System (GMDSS).
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.
DOLLY WHEEL – A rolling jack assembly at the front of the trailer used for positioning the coupler during trailer hookup.
DRAFT – The depth of the boat below the waterline, measured vertically to the lowest part of the hull.


EBB – A receding current.
ELECTRONIC LEAKAGE CIRCUIT INTERRUPTER (ELCI) – Installed with or in addition to the main shore power disconnect circuit breaker(s) to offer an additional level of protection from shore power faults.
ELECTRONIC NAUTICAL CHARTS (ENCS) – Vector data sets that support all types of marine navigation.
ELECTROLYSIS – The breakup of metals due to the effects of galvanic corrosion.
EMERGENCY POSITION INDICATING RADIO BEACONS (EPIRBS) – Safety devices carried by vessels to alert search and rescue services and allow them to quickly locate you in the event of an emergency.


FATHOM – Six feet.
FENDERS – Objects placed alongside the boat for cushioning. Sometimes called bumpers.
FIGURE EIGHT KNOT – A knot in the form of figure eight, placed at the end of a line to prevent the line from passing through a grommet or a block.
FLARE – The outward curve of a vessel’s sides near the bow. A distress signal.
FLOOD – A incoming current.
FLUKE – The palm of an anchor.
FOLLOWING SEA – An overtaking sea that comes from astern.
FORE – Toward the front or bow of the boat. Opposite of aft.
FREEBOARD – The distance from the water to the gunwale.
FUEL SENDING UNIT – The electrical device that is mounted on the outside of a built-in fuel tank and controls the dashboard fuel gauge.


GALLEY – The kitchen area of a boat.
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 – (1) Term for the boat that must take whatever action necessary to keep well clear of the boat with the right-of-way in meeting or crossing situations. (2) The burdened boat.
GLOBAL MARITIME DISTRESS AND SAFETY SYSTEM (GMDSS) – An internationally agreed-upon set of safety procedures, types of equipment, and communication protocols used to increase safety and make it easier to rescue distressed ships, boats, and aircraft.
GLOBAL POSITIONING SYSTEM (GPS) – A global navigation satellite system that provides geolocation and time information to a GPS receiver.
GROUND FAULT CIRCUIT INTERRUPTER (GFCI) – A type of circuit breaker that measures current flow in the hot and neutral wires and immediately switches the electricity off if an imbalance of current flow is detected.
GUNWALE – The rail or upper edge of a boat’s side.


HEAD – A marine toilet.
HEADING – The direction in which a vessel’s bow points at any given time.
HEADWAY – The forward motion of a boat. Opposite of stern way.
HELM – The steering wheel or command area.
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 the deck in a large vessel, used solely for carrying cargo.
HULL – The body of the boat.
HYPOTHERMIA – A physical condition where the body loses heat faster than it can produce it.


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.
IN-LINE FUSE – A type of protective fuse located in the power wire of a direct current (DC) circuit usually near the battery.


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.


KEEL – The lowest portion of the boat; extends fore and aft along the boat’s bottom.
KNOT – A measure of speed equal to one nautical mile (6076 feet) per hour.
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.
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.
LIFE JACKET – A buoyant, wearable jacket that, when properly used, will support a person in the water; also see PFD.
LIST – Leaning or tilting of a boat toward the side.
LINE – Rope and cordage used aboard a vessel.
LOG – A record of courses or operations. 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.


MAKING WAY – Making progress through the water.
MARINE CHART – Seagoing maps showing depths, buoys, navigation aids, etc.
MIDSHIP – Approximately in the location equally distant from the bow and stern.
MOORING – An anchor, chain, or similar device that holds a boat in one location.


NATIONAL MARINE ELECTRONICS ASSOCIATION (NMEA) – A U.S.-based marine electronics trade organization setting standards of communication between marine electronics.
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION (NOAA) – An American scientific agency within the United States Department of Commerce that focuses on the conditions of the oceans, major waterways, and the atmosphere.
NAUTICAL – It’s easy to define nautical: it is an all-encompassing word for anything concerning sailors or maritime travel. All of the boat terminologies here can be defined as nautical words.
NAUTICAL MILE – One minute of latitude; approximately 6076 feet – about 1/8 longer than the statute mile of 5280 feet.
NAVIGATION – The art and science of conducting a boat safely from one point to another.
NAVIGATION AID – Recognizable objects on land or sea such as buoys, towers or lights which are used to fix positions to identify safe and unsafe waters.
NMMANational Marine Manufacturers Association.
NO-WAKE SPEED – The speed at which a boat travels to produce an imperceptible wake.


OUTBOARD – Toward or beyond the boat’s sides. A detachable engine mounted on a boat’s stern.
OVERBOARD – Over the side or out of the boat.


PASSIVE HYDRO LOCK – A problem that occurs when water siphons through the boat’s exhaust system, enters a cylinder in the engine and results in an engine starting failure. This problem is possible on any marine vessel powered by a combustible engine with exhaust risers that sit below the waterline.
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, and protection for wharves, piers, etc.; constructed of piles (see PILE)
PILOTING – Navigation by use of visible references, the depth of the water, etc.
PFD – A buoyant personal flotation device used to support a person in the water; also see Life Jacket.
PITOT TUBE – See Speedometer Pickup Tube.
PLANING – A boat is said to be planning when it is essentially moving over the top of the water rather than through the water.
PLANING HULL – A hull designed to lift, thereby reducing friction and increasing efficiency.
PORPOISE – A condition in which the bow bounces up and down caused by trimming the engine too far out.
PORT – (1) The left side of a boat when facing the bow. (2) A destination or harbor.
PRIVILEGED VESSEL – Term used for the boat with the right-of-way.


QUARTER – The sides of a boat aft of amidships.
QUARTERING SEA – Sea coming on a boat’s quarter.


RIGHT-OF-WAY – Term for the boat that has priority in meeting or crossing situations. The stand-on or privileged boat.
RODE – The anchor line and/or chain.
RULES OF THE ROAD – Regulations for preventing collisions on the water.
RUN – To allow a line to feed freely.
RUNNING LIGHTS – Lights are 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 onboard automatic equipment.
SCOPE – Technically, the ratio of the 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 the deck, in the toe rail, or in bulwarks (with drain pipes) in the deck itself.
SEA COCK – A through hull valve, a shut-off on a plumbing or drain pipe between the vessel’s interior and the sea.
SEAMANSHIP – All the arts and skills of boat handling, ranging from maintenance and repairs to piloting, sail handling, marlinespike work, and rigging.
SEA ROOM – A safe distance from the shore or other hazards.
SEAWORTHY – A boat or a boat’s gear able to meet the usual sea conditions.
SECURE – To make fast.
SET – Direction toward which the current is flowing.
SLACK – Not fastened; loose. Also, to loosen.
SOUNDING – A measurement of the depth of water.
SPEEDOMETER PICKUP TUBE – Also called a pilot tube. The plastic device extends below the bottom of the boat. It connects to the speedometer with plastic flexible tubing.
SPLASH WELL – The section of an outboard-equipped boat that is just forward of the transom.
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.
SQUARE KNOTA knot used to join two lines of similar size. Also called a reef knot.
STAND ON VESSEL – Term for the boat that must maintain course and speed in meeting or crossing situations. The privileged boat.
STARBOARD – The right side of the boat when looking toward the bow.
STEM – The forwardmost part of the bow.
STERN – The back of the boat.
STOW – To pack the cargo.
STRONG POINT– A dedicated eye specially reinforced for the attachment of mooring lines, anchor chains, anchor lines, and tow lines.
SURGE BRAKES – A type of trailer braking system designed to automatically actuate when the tow vehicle’s brakes are applied.
SWAMP – To fill with water, but not settle to the bottom.


TIDE – The periodic rise and fall of water levels in the oceans.
TILLER – A bar or handle for turning a boat’s rudder or an outboard motor.
TRANSDUCER – The unit that sends/receives signals for the depth sounder.
TRANSOM – The transverse beam across the stern.
TRIM – Fore to aft and side to side balance of the boat when loaded.


UNDERWAY – Boat in motion; i.e., not moored or anchored.
USCGUnited States Coast Guard.


V BOTTOM – A hull with the bottom section in the shape of a “V”.
VISUAL DISTRESS SIGNAL – A device used to signal the need for assistance such as flags, lights, and flares.


WAKE – The waves that a boat leaves behind when moving through the water.
WATERLINE – A line painted on a hull that shows the point to which a boat sinks when it is properly trimmed
WATERWAY – A navigable body of water.
WAY – Movement of a vessel through the water such as headway, sternway, or leeway.
WINDWARD – Toward the direction from which the wind is coming.


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


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