MMSI

Maritime Mobile Service Identity — a unique nine-digit number issued to each DSC-VHF/HF radio, EPIRB, or AIS transponder, used to identify the vessel in digital distress and routine calls.

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Related M-terms

Mizzenmast

The shorter mast stepped aft of the mainmast on a ketch or yawl.

Marlinspike

A tapered metal spike used to loosen knots, open rope lays, and work splices.

MFD

Multi-Function Display — a large chartplotter screen able to show radar, AIS, sonar, engin…

Magnetic

Referring to the magnetic north pole rather than true geographic north.

Mast

The vertical spar — originally timber, today commonly aluminium or carbon — from which the…

MOB button

A dedicated button on a GPS, chartplotter, or autopilot that marks the current position th…

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