A glossary of nautical terms - Deep Blue Sea Training (2024)

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A glossary of nautical terms

Each month, we will add nautical terms to this list in alphabetical order. This is a partial glossary of nautical terms; some remain current, while many date from the 17th to 19th centuries.

A to C - D to F - G to I - J to L - M to O

M

• Mae West - A Second World War personal flotation device used to keep people afloat in the water; named after the 1930s actress Mae West, well known for her large bosom.
• Magnetic bearing - An absolute bearing using magnetic north.
• Magnetic north - The direction towards the North Magnetic Pole. Varies slowly over time.
• Main deck - The uppermost continuous deck extending from bow to stern.
• Mainbrace - One of the braces attached to the mainmast.
• Mainmast (or Main) - The tallest mast on a ship.
• Mains - The main brails on the mainsail.
• Mainsheet - Sail control line that allows the most obvious effect on mainsail trim. Primarily used to control the angle of the boom, and thereby the mainsail, this control can also increase or decrease downward tension on the boom while sailing upwind, significantly affecting sail shape. For more control over downward tension on the boom, use a boom vang.
• Mainstay - The stay running from the top of the mainmast to the bottom of the foremast, or from the top of the foremast to the ship's stem.
• Making way - When a vessel is moving under its own power.
• Man-of-war or man o' war - a warship from the Age of Sail.
• Man overboard! - An emergency call that alerts the crew that someone aboard has gone overboard and must be rescued.
• Man the rails - To station the crew of a naval vessel along the rails and superstructure of the vessel as a method of saluting or rendering honors.
• Man the yards - To have all of the crew of a sailing vessel not required on deck to handle the ship go aloft and spread out along the yards. Originally used in harbors to display the whole crew to the harbor authorities and the other ships present to show that the vessel's guns were not manned and hence her intentions were peaceful, manning the yards has since became a display used in harbor during celebrations and other special events.
• Manifest - A document listing the cargo, passengers, and crew of a ship for the use of customs and other officials.
• Marconi rig - Another term for Bermudan rig. The mainsail is triangular, rigged fore-and-aft with the lead edge fixed to the mast. Refers to the similarity of the tall mast to a radio aerial.
• Marina - a docking facility for small ships and yachts.
• Marine - 1. A soldier trained for service afloat in a (primarily) infantry force that specializes in naval campaigns and subordinated to a navy or a separate naval branch of service rather than to an army. Often capitalized (e.g., "a Marine," or "the Marines"). Notable examples are the United Kingdom's Royal Marines, formed as the Duke of York and Albany's Maritime Regiment of Foot in 1664 with many and varied duties including providing guard to ship's officers should there be mutiny aboard, and the US Marine Corps, formed in 1775 as a separate naval service alongside the US Navy. It is incorrect, and often viewed by marines as offensive, to refer to a marine as a "soldier" or "infantryman," as these terms refer to personnel of an army rather than those of a marine force. It also is incorrect, and sometimes considered offensive by both merchant mariners and marines, to refer to merchant mariners as "merchant marines," because merchant mariners are civilian sailors responsible for operating merchant ships and are not marines. Marines sometimes are thought by seamen to be rather gullible, hence the phrase "tell it to the marines," meaning that one does not believe what is being said. 2. An alternative term for a navy, uncommon in English, but common in other languages. 3. Of, or pertaining to, the sea (e.g, marine biology, marine insurance, marine life, marine salvage). 4. A painting representing a subject related to the sea.
• Mariner - A sailor.
• Maritime - 1. Of or related to the sea (e.g., maritime activities, maritime law, maritime strategy). 2. Bordering on the sea (e.g., maritime provinces, maritime states). 3. Living in or near the sea (e.g., maritime animals). 4. Of or relating to a mariner or sailor.
• Marlinspike - A tool used in ropework for tasks such as unlaying rope for splicing, untying knots, or forming a makeshift handle.
• Mast - A vertical pole on a ship which supports sails or rigging. If a wooden, multi-part mast, this term applies specifically to the lowest portion.
• Mast case - A yatchsmans tabernacle. The iron fitting in which the heel of the mast is mounted.
• Mast stepping - The process of raising the mast.
• Masthead - A small platform partway up the mast, just above the height of the mast's main yard. A lookout is stationed here, and men who are working on the main yard will embark from here.
• Master - 1. The captain of a commercial vessel. 2. A senior officer of a naval sailing ship in charge of routine seamanship and navigation but not in command during combat. 3. Master, a former naval rank.
• Master-at-arms - A non-commissioned officer responsible for discipline on a naval ship. Standing between the officers and the crew, commonly known in the Royal Navy as 'the Buffer'.
• Matelot - A traditional Royal Navy term for an ordinary sailor.
• Material - Military equipages of all descriptions for the naval services. The bombs, blankets, beans and bulletins of the Navy and Marine Corps. Taken from Nelson's British navy as the US services became professional. Related: Materiel – the military equipages of the Army and Air Force, taken from Napoleon's French army as the US services became professional.
• Merchant marine - A collective term for all merchant ships registered in a given country and the civilians (especially those of that nationality) who man them; the ships and personnel in combination are said to constitute that country's merchant marine. Called the merchant navy in the United Kingdom and some other countries.
• Merchant mariner - A civilian officer or sailor who serves in the merchant marine. Sometimes such personnel are incorrectly called "merchant marines," but both merchant mariners and marines frown on this term; although merchant mariners are part of the merchant marine, they are civilians and are not in any way marines, which are a specialized type of military personnel.
• Merchant navy - A name bestowed upon the merchant marine of the United Kingdom by King George V, and since adopted by some other countries as well; the merchant navy's personnel are civilians, and the term "merchant navy" does not imply that they or their ships are a part of the navy. Synonymous with the term merchant marine.
• Merchantman - Any non-naval passenger or cargo-carrying vessel, including cargo ships, tankers, and passenger ships but excluding troopships.
• Mess or messdeck - 1. An eating place aboard ship. 2. A group of crew who live and eat together.
• Mess deck catering - A system of catering in which a standard ration is issued to a mess supplemented by a money allowance which may be used by the mess to buy additional victuals from the puss*r's stores or elsewhere. Each mess was autonomous and self-regulating. Seaman cooks, often members of the mess, prepared the meals and took them, in a tin canteen, to the galley to be cooked by the ship's cooks. As distinct from "cafeteria messing" where food is issued to the individual hand, which now the general practice.
• Metacenter - The midway point between a vessel's center of buoyancy when upright and her center of buoyancy when tilted.
• Metacentric height (also GM) - A measurement of the initial static stability of a vessel afloat, calculated as the distance between her centre of gravity and her metacenter. A vessel with a large metacentric height rolls more quickly and therefore more uncomfortably for people on board; a vessel with a small metacentric height will roll sluggishly and may face a greater danger of capsizing.
• Middles - The middle brails on the mainsail, higher than the lowers, and lower than the mains.
• Midships - The middle section of a vessel with reference to the longitudinal plane, as distinguished from fore or aft.
• Midshipman - 1. During the 17th century, a naval rating for an experienced seaman. 2. From the 18th century, a naval commissioned officer candidate. 3. From the 1790s, an apprentice naval officer. 4. From the 19th century, an officer cadet at a naval academy. 5. In contemporary British usage, a non-commissioned officer below the rank of lieutenant. Usually regarded as being "in training" to some degree. Also known as 'Snotty'. 'The lowest form of rank in the Royal Navy' where he has authority over and responsibility for more junior ranks, yet, at the same time, relying on their experience and learning his trade from them. 6. In contemporary American usage, a cadet of either sex at the US Merchant Marine Academy or the US Naval Academy. When plural (Midshipmen), the term refers to the student body of either academy, and more formally as "the Regiment of Midshipmen" for the US Merchant Marine Academy and "the Brigade of Midshipmen" for the US Naval Academy. Midshipmen also is the name of the US Naval Academy's sports teams.
• Midshipman's hitch - An alternative to the Blackwall hitch, preferred if the rope is greasy. Made by first forming a Blackwall hitch and then taking the underneath part and placing over the bill of the hook.
• Midshipman's nuts - Broken pieces of biscuit as dessert.
• Midshipman's roll - A slovenly method of rolling up a hammock transversely, and lashing it endways by one clue.
• Military mast - Hollow tubular masts used in warships in the last third of the 19th century, often equipped with a fighting top armed with light-caliber guns.
• Mine - A self-contained explosive device intended to damage or sink surface ships or submarines, designed to be placed in water and left to wait until they are triggered by the approach of, proximity of, or contact with, a surface ship or submarines.
• Minehunter - A vessel designed or equipped to detect and destroy individual mines. It differs from a minesweeper, which is designed or equipped to clear areas of water of mines without necessarily detecting them first.
• Minelayer - A vessel designed or equipped to deploy ("lay") mines.
• Minesweeper - A vessel designed or equipped to clear areas of water of mines without necessaril detecting them first. It differs from a minehunter, which is designed or equipped to detect and destroy individual mines.
• Mizzen - 1. A mast on a ketch or yawl, or spritsail barge It can be sloop, gaff of spritsail rig, its posioing affore of abaft the steering post defines the difference between a yawl and a ketch. On a barge its rig determines if she is a muffie or a mulie. 2. A staysail on a ketch or yawl, usually lightweight, set from, and forward of, the mizzen mast while reaching in light to moderate air.
• Mizzenmast (or Mizzen) - The third mast, or mast aft of the mainmast, on a ship.
• Mole - A massive structure, usually of stone or concrete, used as a pier, a breakwater, or a causeway between places separated by water. May have a wooden structure built upon it and resemble a wooden pier or wharf, but a mole differs from a pier, quay, or wharf in that water cannot flow freely underneath it.
• Monitor - 1. A turreted ironclad warship of the second half of the 19th century characterized by low freeboard, shallow draft, poor seaworthiness, and heavy guns, intended for riverine and coastal operations. 2. In occasional 19th-century usage, any turreted warship. 3. A shallow-draft armored shore bombardment vessel of the first half of the 20th century, designed to provide fire support to ground troops, often mounting heavy guns. 4. Breastwork monitor: A 19th-century monitor designed with a breastwork to improve seaworthiness. 5. River monitor: A monitor specifically designed for riverine operations, used during the 19th and 20th centuries and more recently than other types of monitor. River monitors generally are smaller and lighter than other monitors.
• Monkey bridge - A high platform above the wheelhouse offering better visibility to the operator while maneuvering.
• Monkey's fist - a ball woven out of line used to provide heft to heave the line to another location. The monkey fist and other heaving-line knots were sometimes weighted with lead (easily available in the form of foil used to seal e.g. tea chests from dampness) although Clifford W. Ashley notes that there was a "definite sporting limit" to the weight thus added.
• Moor - 1. To attach a boat to a mooring buoy or post. 2. To dock a ship. 3. To secure a vessel with a cable or anchor.
• Mooring, also Moorings - A place to moor a vessel.
• Mother ship (also mothership and mother-ship) - A vessel which leads, serves, or carries smaller vessels, in the latter case either releasing them and then proceeding independently or also recovering them after they have completed a mission or operation. A mother ship sometimes contrasts with a tender, which often (but not necessarily) is a vessel that supports or cares for larger vessels.
• Mould - A template of the shape of the hull in transverse section. Several moulds are used to form a temporary framework around which a hull is built.
• Mould loft - Where the lines of the ship are drawn out full-size and the templates for the timbers are made.
• Mousing - Several turns of light line around the mouth of a hook, to prevent unhooking accidents.
• Mulie - A barge rigged with a spritsail main, and a large gaff rigged mizzen afore the steering wheel. It is sheeted to the saddle chock.
• Multipurpose vessel - A cargo ship that has fittings to carry standard shipping containers and retractable tweendecks that can be moved out of the way so that the ship can carry bulk cargo.
• Muster Station - The location on a vessel a person goes either during an emergency or a drill to prepare for one. i.e. A Muster Drill. If a person is believed missing, all hands would report to their muster station for a head count.
• Muzzle - Iron ban around the mast to hold the heel of the sprit.
• M.V. (or MV) - Prefix for "Motor Vessel", used before a ship's name.
• M.Y. (or MY) - Prefix for "Motor yacht", used before a yacht's name.

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