The maritime industry maintains specialised terminology that distinguishes operational meanings from their colloquial usage. This maritime glossary records the most frequently used terms in our publications, with definitions calibrated to commercial port operations rather than to recreational or naval usage. Definitions are written for accessibility to readers without prior maritime industry background.

Bollard Pull

Standardised measure of a tug's pulling force, expressed in tonnes or kilonewtons. Used to determine appropriate tug allocation for vessel manoeuvring under varying wind and current conditions.

Breakbulk

Cargo that is not containerised, not in bulk form, and not on wheels — typically loaded and discharged piece by piece. Includes steel products, paper rolls, machinery, and project cargo.

Bunker Fuel

Marine fuel used to power ship engines. Heavy Fuel Oil (HFO) remained the dominant grade until the IMO 2020 sulphur cap, since when Very Low Sulphur Fuel Oil (VLSFO) and Marine Gas Oil (MGO) have grown in share.

Bunkering

The operation of delivering marine fuel to a ship. May be conducted alongside the quay, at anchor by barge (ship-to-ship), or directly from a shoreside terminal.

Capesize

A class of dry bulk carrier too large to transit the Suez or Panama Canals in their fully-laden state. Capesize vessels carry primarily iron ore and coal cargoes on round-the-Cape routes; typical deadweight is 150,000 to 400,000 tonnes.

DWT

Deadweight Tonnage. The total carrying capacity of a vessel including cargo, fuel, fresh water, stores, crew, and passengers, measured in tonnes.

Feeder

A small or medium container vessel operating short-sea services that distribute or collect containers between a transshipment hub (such as Algeciras) and regional destination ports.

Gantry Crane

A large dockside crane used to load and unload containers from ships. Ship-to-shore (STS) gantry cranes work the ship; rubber-tyred gantry (RTG) and rail-mounted gantry (RMG) cranes work the container yard.

GT

Gross Tonnage. A volumetric measure of the internal capacity of a vessel, expressed as a dimensionless number. Used as the basis for many regulatory and port-dues calculations.

Hinterland

The geographic territory served by a port through its inland transport connections — the area for which the port is the commercial gateway. The hinterland of a port may be exclusive (no competing port serves it) or contested.

ISPS Code

International Ship and Port Facility Security Code — IMO SOLAS framework for security in commercial shipping and at port facilities. Adopted post-September 2001; effective from July 2004.

MARPOL

International Convention for the Prevention of Pollution from Ships — IMO framework comprising six Annexes covering oil, noxious liquids, harmful substances in packaged form, sewage, garbage, and air pollution.

Mooring

The process of securing a vessel alongside a berth, conducted by linehandlers using designated mooring lines passed to bollards or cleats on the quay.

New Panamax

A container vessel sized to the maximum dimensions of the post-2016 expanded Panama Canal locks: approximately 366 m length, 49 m beam, 15.2 m draft, carrying up to 14,500 TEU.

Panamax

A container or bulk vessel sized to the maximum dimensions of the original (pre-2016) Panama Canal locks: approximately 294 m length, 32.3 m beam, 12 m draft. Container Panamax vessels typically carry 4,500 TEU.

Pilotage

The provision of navigational guidance to vessels entering, leaving, or moving within a port. Conducted by licensed maritime pilots with detailed knowledge of local navigation. Compulsory for commercial vessels above set thresholds in most major ports.

Pilot Boat / Pilot Launch

A small fast vessel used to transport pilots between the pilot station and the inbound or outbound vessel. Operates day and night in nearly all weather conditions.

Post-Panamax

A container vessel too large to transit the original Panama Canal — that is, exceeding approximately 32.3 m beam. Includes vessels from approximately 5,000 TEU upward.

Reefer

A refrigerated shipping container used to transport temperature-controlled cargo. Reefer plug positions in a container yard or on a vessel provide the electrical power required to maintain set temperature.

RoRo

Roll-on/Roll-off — vessels designed for the embarkation of wheeled cargo (trailers, automobiles, agricultural and construction machinery) under its own power, by way of stern, side, or bow ramps.

RoPax

A combined Roll-on/Roll-off and passenger vessel. The principal Strait of Gibraltar ferry vessels operate in this configuration.

SOLAS

International Convention for the Safety of Life at Sea — the principal IMO framework for vessel safety standards. First version adopted in 1914 following the loss of RMS Titanic; current version dates from 1974, regularly amended.

STS

Ship-to-Ship transfer — the transfer of cargo, typically liquid bulk or container, between two vessels at anchor or under way. Also used as an abbreviation for Ship-to-Shore (cranes).

Suezmax

A class of tanker sized to the maximum draft of the Suez Canal. Typical deadweight is 120,000 to 200,000 tonnes.

TEU

Twenty-foot Equivalent Unit — the standard measure of container volume, equal to one 20-foot ISO container. A 40-foot container counts as 2 TEU. Container vessel and terminal capacity are quoted in TEU.

Transshipment

The transfer of cargo from one vessel to another within a port, with no movement of the cargo into the local hinterland. The principal commercial function of Algeciras and competing Strait-of-Gibraltar ports.

TSS

Traffic Separation Scheme — an IMO-mandated routeing arrangement that separates vessels travelling in opposite directions in a congested waterway. The Strait of Gibraltar TSS separates east-bound and west-bound deep-sea traffic into designated lanes.

ULCV

Ultra-Large Container Vessel — typically defined as a container vessel of more than 14,500 TEU capacity. Vessels of 18,000 to 24,000 TEU are routinely deployed on the Asia–Europe trade lane and call at Algeciras for transshipment.

VLCC

Very Large Crude Carrier — a tanker of approximately 200,000 to 320,000 deadweight tonnes, used principally for long-haul crude oil transport. VLCCs deliver crude oil to the Cepsa refinery at San Roque.

VTS

Vessel Traffic Service — a system of monitoring, communication, and traffic management operated by port and coastal state authorities. The Strait of Gibraltar VTS is operated jointly by Spanish and Moroccan authorities under the designation Tarifa Traffic.