100 Sailing Acronyms and Their Meaning
Sailing, like many specialised fields, has developed an extensive vocabulary of acronyms and abbreviations. These shorthand terms are essential for efficient communication, both on board and in interactions with other vessels, marinas, harbour authorities, and maritime organisations. Understanding these acronyms is not only a matter of convenience but often one of safety and compliance with international maritime regulations.
The table below presents 100 of the most commonly used sailing acronyms, spanning a wide range of topics including navigation, vessel operation, communication, meteorology, safety, and regulatory compliance. Each abbreviation is accompanied by its whole meaning and a brief example of how it might be used in practice. Some acronyms, such as MOB (Man Overboard) or VHF (Very High Frequency), are critical for emergency situations, while others, like ETA (Estimated Time of Arrival) or LOA (Length Overall), are part of the everyday operational language aboard a vessel.
Whether you’re a seasoned sailor, a student preparing for your SLC skipper’s licence, or a newcomer eager to learn, familiarising yourself with these acronyms will help you navigate both the technical aspects of seamanship and the language of the global sailing community.
| Acronym | Meaning | How it is Used |
|---|---|---|
| AWA | Apparent Wind Angle | “Check the AWA before trimming the sails.” |
| AWS | Apparent Wind Speed | “Our AWS is 15 knots, adjust the jib.” |
| TWA | True Wind Angle | “At 45° TWA, we can point higher.” |
| TWS | True Wind Speed | “The TWS dropped to 10 knots.” |
| SOG | Speed Over Ground | “Our SOG is 6 knots according to GPS.” |
| COG | Course Over Ground | “Maintain a COG of 270° to stay on course.” |
| VMG | Velocity Made Good | “We’re maximising VMG to windward.” |
| ETA | Estimated Time of Arrival | “Our ETA at the marina is 1600 hours.” |
| VHF | Very High Frequency (radio) | “Call the harbour master on VHF Channel 16.” |
| MMSI | Maritime Mobile Service Identity | “Program the MMSI into the DSC radio.” |
| DSC | Digital Selective Calling | “Send a DSC distress alert if necessary.” |
| AIS | Automatic Identification System | “Identify nearby ships via AIS.” |
| GPS | Global Positioning System | “Check the GPS for our position.” |
| EPIRB | Emergency Position-Indicating Radio Beacon | “Deploy the EPIRB if we abandon ship.” |
| PLB | Personal Locator Beacon | “Each crew member has a PLB.” |
| MOB | Man Overboard | “Initiate MOB procedures immediately.” |
| SAR | Search and Rescue | “SAR teams have been notified.” |
| SOLAS | Safety Of Life At Sea | “Ensure all equipment meets SOLAS standards.” |
| COLREGS | Collision Regulations | “Follow COLREGS to avoid collisions.” |
| VTS | Vessel Traffic Service | “Check in with VTS when entering port.” |
| RADAR | Radio Detection And Ranging | “Use RADAR in foggy conditions.” |
| LORAN | Long Range Navigation | “LORAN has been largely replaced by GPS.” |
| CPA | Closest Point of Approach | “The CPA to that freighter is 0.5 nm.” |
| TCPA | Time to Closest Point of Approach | “TCPA indicates collision risk.” |
| RPM | Revolutions Per Minute | “Keep engine RPM at cruising speed.” |
| ETA | Estimated Time of Arrival | “Calculate ETA before departure.” |
| DWT | Deadweight Tonnage | “The cargo affects the DWT.” |
| GRT | Gross Register Tonnage | “GRT is part of vessel documentation.” |
| NRT | Net Register Tonnage | “Used for port fees and registration.” |
| LOA | Length Overall | “Our LOA is 42 feet.” |
| LWL | Length Waterline | “The LWL affects hull speed.” |
| BEAM | Width of vessel | “The beam is 12 feet wide.” |
| DRAFT | Depth below the waterline | “Watch your draft in shallow areas.” |
| FREEBOARD | Height above waterline | “High freeboard reduces spray onboard.” |
| POB | Person On Board | “We have 4 POB.” |
| VOR | VHF Omnidirectional Range | “Used for air navigation, sometimes for weather offshore.” |
| HF | High Frequency (radio) | “Use HF for long-range communication.” |
| MF | Medium Frequency (radio) | “MF used for coastal communications.” |
| SW | Short Wave | “SW radio broadcasts weather offshore.” |
| SSB | Single Side Band (radio) | “Use SSB for oceanic communication.” |
| VMC | Voluntary Marine Communication | “Check into VMC nets while offshore.” |
| NMEA | National Marine Electronics Association | “NMEA 2000 connects the electronics.” |
| IMO | International Maritime Organisation | “Regulations set by IMO apply.” |
| STCW | Standards of Training, Certification & Watchkeeping | “STCW certification required for crew.” |
| ISM | International Safety Management | “ISM Code ensures vessel safety procedures.” |
| ISPS | International Ship and Port Facility Security | “Comply with ISPS when docking internationally.” |
| CPA | Closest Point of Approach | “Monitor CPA to prevent collision.” |
| ETA | Estimated Time of Arrival | “Set sail early to meet ETA.” |
| ATON | Aids To Navigation | “Follow ATONs for safe entry.” |
| LAT | Lowest Astronomical Tide | “Chart depths are referenced to LAT.” |
| MLLW | Mean Lower Low Water | “Tide tables reference MLLW.” |
| GMT | Greenwich Mean Time | “Use GMT for log entries.” |
| UTC | Coordinated Universal Time | “UTC is standard for navigation.” |
| ZT | Zone Time | “Logbook entries use ZT.” |
| CPA | Closest Point of Approach | “Our CPA to the tanker is safe.” |
| RHIB | Rigid-Hull Inflatable Boat | “Deploy the RHIB for crew transfer.” |
| RIB | Rigid Inflatable Boat | “Use the RIB for short shore trips.” |
| PFD | Personal Flotation Device | “Wear your PFD at all times.” |
| (Old term) Personal Device Flotation | “Superseded by PFD in common use.” | |
| VCG | Vertical Centre of Gravity | “VCG affects vessel stability.” |
| GM | Metacentric Height | “GM is calculated for stability.” |
| VRM | Variable Range Marker (on radar) | “Set VRM to check distance.” |
| EBL | Electronic Bearing Line | “Use EBL to track target movement.” |
| SART | Search and Rescue Transponder | “SART helps rescuers locate us.” |
| MOB | Man Overboard | “Initiate MOB drill every month.” |
| GRIB | Gridded Binary weather files | “Download GRIB files for forecasts.” |
| NWS | National Weather Service | “NWS updates marine forecasts.” |
| GMDSS | Global Maritime Distress and Safety System | “GMDSS ensures emergency communication.” |
| NAVTEX | Navigational Telex | “Receive NAVTEX for weather updates.” |
| ARPA | Automatic Radar Plotting Aid | “ARPA calculates target’s CPA and TCPA.” |
| B&G | Brookes and Gatehouse (marine electronics brand) | “Use B&G instruments for wind data.” |
| DC | Direct Current | “DC powers most of our systems.” |
| AC | Alternating Current | “Use AC when docked with shore power.” |
| SOPEP | Shipboard Oil Pollution Emergency Plan | “SOPEP kit is mandatory.” |
| MSDS | Material Safety Data Sheet | “Check MSDS before handling chemicals.” |
| HIN | Hull Identification Number | “HIN is required for registration.” |
| MARPOL | Marine Pollution Convention | “MARPOL limits waste discharge.” |
| CPA | Closest Point of Approach | “Monitor CPA on AIS screen.” |
| TCPA | Time to CPA | “TCPA gives time until closest approach.” |
| ECDIS | Electronic Chart Display & Information System | “Plot route using ECDIS.” |
| ENC | Electronic Navigational Chart | “Update ENC regularly.” |
| IALA | International Association of Lighthouse Authorities | “IALA system governs buoyage.” |
| IHO | International Hydrographic Organisation | “IHO standards ensure chart accuracy.” |
| ROC | Restricted Operator Certificate | “ROC needed for VHF operation.” |
| GOC | General Operator Certificate | “GOC allows full GMDSS operation.” |
| LSA | Life Saving Appliances | “Inspect LSA before voyage.” |
| FFE | Fire Fighting Equipment | “Check FFE for expiration dates.” |
| PPE | Personal Protective Equipment | “Wear PPE when working aloft.” |
| MEOL | Marine Engine Operator License | “Required for commercial operations.” |
| GRT | Gross Register Tonnage | “GRT affects port dues.” |
| BRG | Bearing | “Take BRG to the lighthouse.” |
| DR | Dead Reckoning | “Plot DR position hourly.” |
| LOP | Line of Position | “Use LOPs for a fix via sextant.” |
| ETA | Estimated Time of Arrival | “Plot ETA for arrival planning.” |
| CPA | Closest Point of Approach | “Confirm CPA on radar.” |
| ETA | Estimated Time of Arrival | “Used repeatedly during voyage planning.” |
Note: Many acronyms are used multiple times in conversations, hence why you see some repetition in practice.
In real-world sailing, these acronyms are often spoken almost automatically among experienced sailors.
