nautical adverb

Definition of Abaft

Abaft refers to a position at or towards the stern or back of a boat. It’s a term used by sailors or boat operators to give the direction of a boat. It’s also used by the United States Coast Guard to set safety requirements for marine navigation.

For example, rule 13 on overtaking states, “A vessel shall be deemed to be overtaking when coming up with another vessel from a direction more than 22.5 degrees abaft the beam."

Perhaps the most pertinent use of the term “abaft”, per Apex Lighting’s expertise, is in describing the location of navigation lights and their appropriate beam angles.

Here are a few examples:

LED Masthead Lamp from Apex Lighting

The masthead light (pictured above), is placed over the fore and aft centerline of the vessel, and is fixed to show the light from right ahead to 22.5 degrees abaft the beam on either side of the vessel.

Deck Mount LED Navigation Lamp Kit from Apex Lighting

Sidelights, (pictured above), each showing an unbroken light over an arc of the horizon of 112.5 degrees, are fixed so as to show the light from right ahead to 22.5 degrees abaft the beam on each side.

Below is a bird’s-eye view diagram of the different parts of a boat. Note abaft is an arrow pointing towards the back of the boat.

labeled diagram of a boat

Example of Abaft in a sentence

“The captain asked the crew to move abaft the mainmast to balance the weight distribution of the boat.”

Synonyms: aft, behind, astern, back, backward, hind

Related Terms for Abaft