air brake

WordReference Random House Learner's Dictionary of American English © 2026

ˈair ˌbrake, n. [countable]

1. Mechanical Engineering a brake operated by compressed air:
   a large truck with air brakes.

WordReference Random House Unabridged Dictionary of American English © 2026

air′ brake′, 

1. Mechanical Engineering a brake or system of brakes operated by compressed air.
2. Aeronautics a device for reducing the air speed of an aircraft by increasing its drag.
3. Mechanical Engineering a device for stopping the sails of a windmill by disrupting the flow of air around them.
• 1870–75, American.

Collins Concise English Dictionary © HarperCollins Publishers::

air brake noun

1. a brake operated by compressed air, esp in heavy vehicles and trains
2. Also called: dive brake an articulated flap or small parachute for reducing the speed of an aircraft