A sheet of gas ejected downward from a jet engine through a slot in the trailing edge of a wing, acting as a flap and so increasing lift at low speeds.
Origin
1950s; earliest use found in The Times.
Definition of jet flap in US English:
jet flap
noun
Aeronautics
A sheet of gas ejected downward from a jet engine through a slot in the trailing edge of a wing, acting as a flap and so increasing lift at low speeds.