Nautical Terms That Begin with the Letter M

May 09, 2023 · 11 mins read ·

Fun Stuff, Maritime Industry
the McDonald's letter M sign

If you’re interested in nautical terms and maritime phrases, you might have been reading our recent collection of blog posts based upon our Martide shipping glossary, in which we’ve covered a whole dictionary’s-worth of words, acronyms and expressions that are all to do with ships, sailing, the merchant navy and more.

To catch up with some of our previous blogs, you might like to check out Nautical Terms That Begin with the Letter A or Nautical Terms That Begin with the Letters E and F.

But for now, we’re going to take a look at maritime terms that begin with the letter M. Let’s do it!

Nautical terms that begin with the letter M


MARPOL, the International Convention for the Prevention of Pollution from Ships as adopted by the IMO is the main international convention covering prevention of pollution of the marine environment by ships from operational or accidental causes.


MMSI stands for Maritime Mobile Service Identity. An MMSI is a nine digit long unique identification number which is sent in digital form over a radio frequency channel in order to ID a vessel. The MMSI relates to the flag country that the ship is sailing under.

Maiden Voyage

A vessel’s first journey it makes after being delivered from the shipyard.

Read more: Nautical Terms That Begin with the Letter B

Main Deck

The Main Deck of a ship is the uppermost continuous deck that extends all the way from fore to aft i.e. from bow to stern.


The Manifest is the Master of the ship’s list of goods and products that make up the vessel’s cargo.

Manning Agency

A Manning Agency or Crewing Agency is a company who works with their client, the shipowner, to find seafarers to work onboard their vessels. 

The Manning Agent checks that the seafarer has the right certifications and documentation for the position, as well as the correct travel documents. The agent also arranges visas and medical checks for the shipowner.

Read more: Nautical Terms That Begin with the Letter C

Marine Surveyor

A shore-based maritime career, a Marine Surveyor is a person who inspects a vessel’s hull or its cargo for damage or quality. 


Maritime as an adjective has a couple of meanings. It can mean situated on or near the sea or refer to commerce or navigation by sea. 

Maritime English

Maritime English is the name given to the language seafarers use at sea. It combines the English language with specific maritime terms and commands (for example, starboard instead of right or aft, meaning towards the rear of the vessel). 

It is used so that seafarers of different native languages can communicate with one another safely and efficiently. A certain level of proficiency in the English language is required by most reputable shipping companies. 

Maritime English is also known as Seaspeak and Standard Marine Communication Phrases or SMCP. 

Read more: Nautical Terms That Begin with the Letter D

Maritime Recruitment

Maritime Recruitment refers to the act of shipowners / employers, crewing officers, recruitment officers and manning agents recruiting and hiring seafarers to work on their vessels at sea. 

This is usually done on a contract basis with seafarers working anything from a few weeks up to months at a time onboard.


The Master, also referred to as the Captain, is the highest rank of seafarer and the person who is ultimately in charge of, and responsible for, the vessel and her cargo, crew and passengers. 

Masthead Light

The Masthead Light is a white light positioned over the fore and aft centreline of a ship.

Read more: Nautical Terms That Begin with the Letters G, H and I

Merchant Marines

The Merchant Marines is the term used to describe the United States of America's commercial shipping operations. (It is called the Merchant Navy in most other countries). 

The vessels in the Merchant Marie's fleet can be anything from cargo and container ships, heavy lift vessels and oil tankers to fishing vessels, ferries and cruise ships.   

Merchant Navy

The Merchant Navy (called the Merchant Marines in the United States) is the term used to describe a country's commercial shipping operations. 

Vessels in a Merchant Navy's fleet can be anything from cargo and container ships, heavy lift vessels and oil tankers to fishing vessels, ferries and cruise ships. 


Depending on the vessel and/or nationality, a Messman might be called a Steward, Steward’s Assistant, General Steward, Galley Utilityman or even Waiter. The Messman is one of the unlicensed Seafarer Ranks and an entry level cargo ship job

The Messman is the go-to person when it comes to anything related to food serving and general hygiene. They help the Cook prepare meals, set tables, serve food, prepare tea, coffee and other drinks and ensure water coolers have a fresh supply of water. 

After meals, they will clear the tables, clean the mess area, and wash the dishes.

Middle Watch

The Middle Watch is the period of being on duty (AKA Watch) that takes place onboard a vessel between 0000hrs and 0400hrs.

Minimum Safe Manning

Sometimes also referred to as Manning Scales or Manning Policy, Minimum Safe Manning is the minimum number of seafarers - including officers and crew - that must be onboard a ship for it to be considered safe to sail. 

The scales are worked out to ensure that there will be sufficient people with sufficient practical ability to meet every possible eventuality at sea.

Mobile Offshore Drilling Unit

 Often abbreviated to MODU, a Mobile Offshore Drilling Unit is a vessel that engages in drilling operations for the exploration (or exploitation) of resources beneath the sea bed. These could include resources such as liquid or gaseous hydrocarbons. 


To Moor is the act of securing a vessel by anchor or to the shore by ropes, lines or chains.

Mooring Line

A Mooring Line is a cable, rope or line used to tie up a ship when at a dock.

Morning Watch

The Morning Watch is the period of being on duty (AKA Watch) that takes place onboard a vessel between 0400hrs and 0800hrs.

Morse Lamp

The Morse Lamp (also called a Signal Lamp or Aldis Lamp) is a hand-held electric lamp which is normally found on the bridge wing of a vessel. It is used to signal Morse code messages via flashing light between ships of all types, including naval and commercial.

Motor Ship

A Motor Ship is any vessel that is propelled by internal combustion engines. Motor Ship is usually abbreviated to MS and used in front of a vessel's name. For example MS Bounty.

Motor Vessel

A Motor Vessel is any ship that is propelled by internal combustion engines. Motor Vessel is usually abbreviated to MV and used in front of a vessel's name. For example MV Bounty.


A Motorman is part of a vessel’s engine department. They stand watch with the Engine Officer on duty and will help with repair and maintenance as well as carry out basic tasks in the engine room and around the vessel such as cleaning or painting. 

They will also have duties that could include making routine checks of machinery, as well as of the bilge and pump rooms, and the tanks. 

They will inspect equipment such as turbines, condensers, and pumps and will be expected to record their findings and report any issues or problems that they find to their Officers, and safely rectify them if possible. 

Multipurpose Ship

A Multipurpose Ship is any kind of vessel that has the ability to carry different types of cargo which require different methods of handling. 

These ships include general cargo ships which can carry regular cargo and dry, loose cargo in containers and RoRo ships which can carry wheeled cargo such as cars and trucks, as well as containers.

Muster Drill

All ships conduct Muster Drills, also known as Lifeboat Drills. A Muster Drill is an onboard exercise to ensure that all crew (as well as any passengers) know how to evacuate the vessel in the event of an emergency. 

International law stipulates that the Master of every ship must make sure that officers, crew and passengers are familiar with the procedure of lowering the lifeboats and evacuating the vessel, and the emergency use of the lifeboats. 

So there you have it. Are there any nautical words or shipping industry phrases that surprised you? Or any that you think we’re missing? If so, drop us a line on social media and we’ll add your suggestions next time we update this blog post!

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Read the previous blog in this series: Nautical Terms That Begin with the Letters J, K and L 

Eve Jones

Eve Jones