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WordNet
dive brake

n. a small parachute or articulated flap to reduce the speed of an aircraft [syn: airbrake]

Wikipedia
Dive brake

In the past dive brakes were mostly used on dive bombers, which needed to dive very steeply, but not exceed their red line speed in order to drop their bombs accurately. The airbrakes or spoilers fitted to gliders often function both as landing aids and to keep the aircraft's speed below its maximum permissible indicated air speed in a vertical dive. Most modern combat aircraft are equipped with air brakes, which perform the same function as dive brakes.