42 terms starting with M.
- Magnetic Bearing
A bearing measured clockwise from magnetic north, requiring correction for variation to obtain a true bearing.
- Magnetic Compass
A compass that aligns with Earth's magnetic field to indicate magnetic north; required as backup on all SOLAS vessels.
- Main Engine (ME)
The primary propulsion engine driving the ship's propeller shaft, typically a large slow-speed two-stroke diesel on cargo ships.
- Mandatory Pilotage
A legal requirement in certain ports or waterways that a licensed pilot must be employed to navigate a vessel through that area.
- Marine Diesel Oil (MDO)
A distillate fuel oil with low sulfur content, used in auxiliary engines and during port operations where ECA rules apply.
- Marine Pollutant (MP)
Substance identified in IMDG Code as harmful to the marine environment; carries the 'Marine Pollutant' (dead-fish-and-tree) mark.
- Marine Superintendent
A senior shore-side manager responsible for the nautical operations, safety, and compliance of vessels in a company fleet.
- Maritime Labour Convention 2006 (MLC)
ILO convention establishing minimum working, living, and social security standards for seafarers worldwide.
- Maritime Rescue Coordination Centre (MRCC)
National coordinating centre that receives distress alerts and orchestrates SAR operations within a defined Search and Rescue Region (SRR).
- Maritime Security Centre — Horn of Africa (MSCHOA)
EU NAVFOR coordination centre supporting BMP transits and convoy escort tasking.
- MARPOL Annex I
The annex of MARPOL regulating prevention of pollution by oil, covering operational discharges and accidental spills from ships.
- MARPOL Annex II
The annex of MARPOL controlling discharge of noxious liquid substances carried in bulk, applicable to chemical tankers.
- MARPOL Annex III
Regulations for the prevention of pollution by harmful substances carried at sea in packaged form.
- MARPOL Annex V
The annex of MARPOL governing disposal of garbage from ships, prohibiting most plastics discharge into the sea.
- MARPOL Annex VI
The annex of MARPOL setting limits on sulphur oxides, nitrogen oxides, and other air pollutant emissions from ships.
- MARPOL Bunker Sample
Representative sample drawn at the bunker manifold during delivery, sealed and retained for 12 months.
- Mast Riser
A large-diameter high-velocity vent pipe fitted to a tanker's mast to discharge cargo vapours safely above ignition sources.
- Master
The certificated officer in overall command of a vessel, legally responsible for the safety of the ship, crew, cargo, and environment.
- Material Safety Data Sheet (MSDS)
A document providing information on the hazards, handling precautions, and emergency procedures for a chemical or dangerous cargo.
- Medical First Aid Guide (MFAG)
IMO/WHO/ILO guide for treating injuries arising from incidents with dangerous goods aboard ship.
- Mercator Sailing
A method of solving rhumb line problems using the properties of a Mercator chart to find course and distance between positions.
- Metacentric Height (GM)
The vertical distance between the centre of gravity (G) and the metacentre (M), the primary indicator of a vessel's initial stability.
- Metacentric Height from Keel (KM)
Vertical distance from keel to the metacentre M; sum of KB (keel to centre of buoyancy) and BM (metacentric radius).
- METAREA
One of twenty-one geographic areas for which meteorological services co-ordinate the broadcast of marine weather forecasts.
- Methanol as Marine Fuel
Liquid alcohol fuel adopted by some newbuild container and tanker fleets; bunkered at ambient temperature, simpler infrastructure than LNG.
- MF/HF SSB
Single-side-band radio in MF (1.6–4 MHz) and HF (4–27 MHz) bands used for medium- and long-range maritime voice and DSC.
- Minimum Safe Manning
Flag-state-issued document specifying the minimum manning by rank/qualification for safe operation of the ship.
- MLC Financial Security — Abandonment
MLC 2014 amendment requiring shipowners to maintain insurance/financial security for repatriation, wages, and essential needs of abandoned seafarers.
- MMSI (Maritime Mobile Service Identity)
Nine-digit numerical address used to identify ships, coast stations, and devices in DSC, AIS, and satellite distress alerting.
- MMSI Number (MMSI)
A nine-digit Maritime Mobile Service Identity used to identify a ship's radio and AIS transmissions uniquely.
- MOB AIS (Man Overboard AIS)
Personal AIS beacon worn by crew that activates on water immersion, broadcasting AIS position reports with an MMSI beginning 972 to identify a man-overboard casualty.
- Moment to Change Trim 1 cm (MCT1cm)
The trimming moment in tonne-metres needed to alter a vessel's trim by one centimetre, used in stability calculations.
- Monsoon
A seasonal reversal of prevailing winds affecting the Indian Ocean and western Pacific, bringing heavy rainfall on its wet phase.
- Moonpool
Vertical opening through the hull of an offshore vessel allowing equipment to be lowered from a sheltered indoor location.
- Mooring
Securing a vessel to a berth, buoy, or anchor using lines, chains, or anchors to keep it stationary.
- Mooring Equipment Guidelines 4 (MEG4)
OCIMF guideline (2018) for mooring system design, operation, and inspection of tankers and gas carriers.
- MoorMaster
Cavotec vacuum mooring system replacing conventional lines in some ferry, container, and bulk berths.
- Motorman
An engine room rating who assists engineers with machinery operation, maintenance, and watchkeeping duties.
- MSI (Maritime Safety Information)
Umbrella term for navigational warnings, meteorological forecasts, distress relays, SAR information, and piracy reports broadcast to ships under the GMDSS framework.
- Multipurpose Support Vessel (MPSV)
OSV combining DP, large deck, crane, ROV, and accommodation for varied subsea/inspection/maintenance work.
- multipurpose vessel (MPP)
Versatile geared cargo ship carrying containers, breakbulk, project cargo, and heavy lifts in a single voyage, typically 3 000–15 000 DWT.
- Muster Station
A designated assembly point where crew and passengers gather when an emergency alarm is sounded prior to abandoning ship.