Marine and Boat Acronyms and Abbreviations

Published: April/May 2013

When a reader wrote in complaining that the many initials, abbreviations, and acronyms in electronics articles nowadays leaves him baffled, we set about clearing things up.

Below is a list of acronyms we’ve been guilty of using in the past. If there are other marine abbreviations you need an explanation for, email us and we’ll do our best to answer.

AIS: Automatic Identification System (displays real-time ship and marine traffic positions)

APP: Not strictly an acronym, but shorthand for application (for mobile phones and tablets)

AWA: Anchor Watch Alarm

CPA: Closest Point of Approach, the predicted minimum distance between your vessel and a target on radar or AIS if you both continue at present course and speed

DSC: Digital Selective Calling (allows a distress signal to be sent from a VHF)

DSM: Digital Sounder Module, also called a black box in some cases, a microprocessor dedicated to interpreting and improving sonar displays on your fishfinder

EBL: Electronic Bearing Line, bearing to a target as displayed on a radar screen OR Exposed Location Buoy if you’re talking aids to navigation

EPIRB: Emergency Position Indicating Radio Beacon (used to alert services in an emergency)

GPS: Global Positioning System (a satellite navigation system providing location and time)

IP: Internet Protocol, just a name for how devices speak to each other

LCD: Liquid crystal display, just another way of making images appear on a screen

MFD: Multi-function display. Your chartplotter, can do more than show you charts, hence the "multi" part

MFI: Depending on where you see it, it could be Made for Apple (iPhone, iPad, etc) or Multi-port fuel injection, if you’re talking engines

MMSI: Maritime Mobile Service Identity (the number that identifies your boat. Important in an emergency. Register your MMSI number at

MOB: Man Overboard

NMEA: National Marine Electronics Association

PLB: Personal Locator Beacon (portable transmitter capable of sending an emergency distress signal)

RTE: Route, in shorthand, or Radar Target Enhancer if you are being fancy with your radar reflector

VHF: Very High Frequency, the designation for the frequency bandwidth that marine radios operate on. Specifically from 156-163 MHz. Distinct from UHF (Ultra High Frequency) where cordless phones and baby monitors work

VRM: Variable Range Marker, the rings on a radar display that indicate distances from your vessel at the center


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