Definition
Hinged surfaces on the rear (trailing) edge of the wing that the pilot can extend downward to increase lift and drag at lower airspeeds, primarily used during takeoff, approach, and landing.
Plain English
Movable panels on the back edge of the wing that fold down to help the airplane fly more slowly without stalling, especially when taking off or landing.
Context Anchor
You encounter trailing-edge flaps during preflight checks, takeoff and landing checklists, and while changing the airplane’s setup for slower flight near the runway.
Derivation
Trailing edge is the rear edge of the wing -- the edge the air leaves last as it flows over the wing. Flap comes from the idea of a hinged piece that can be folded or swung down. So a trailing-edge flap is literally a hinged piece on the back edge of the wing.
Why Pilots Care
They reduce stall speed and runway length needed for safe takeoff and landing.
Intuition Check
“Flaps” here does not mean something loose that flaps in the wind. It means controlled wing panels that move to a selected position. “Trailing-edge” does not mean the flap is dragging behind the airplane. It means the flap is located on the rear edge of the wing.
Example Sentence 1
On final approach, the pilot extended full trailing-edge flaps to slow the airplane and steepen the descent toward the runway.
Example Sentence 2
Partial trailing-edge flaps were used on takeoff to improve climb performance.