Definition
Movable panels on the upper surface of the wing that, when raised into the airflow, disrupt (spoil) the smooth flow of air over the wing. This reduces lift and increases drag. Spoilers are used to descend rapidly without gaining airspeed, to slow the airplane after touchdown, and on some aircraft to assist with roll control.
Plain English
Flat panels on top of the wing that pop up to interrupt the airflow. When they come up, the wing makes less lift and the airplane slows down or descends more quickly.
Context Anchor
Seen in flight-control and level-flight discussions, especially when describing how some airplanes control roll or reduce lift after touchdown.
Derivation
From the verb 'spoil,' meaning to ruin or interfere with. The panels literally spoil the smooth airflow over the wing that would otherwise produce lift.
Why Pilots Care
They allow a controlled descent without excessive airspeed buildup and provide aerodynamic braking after touchdown, shortening the landing roll.
Intuition Check
A spoiler is not a cosmetic part, and it does not mean something is broken. In aviation, a spoiler is a movable wing panel used on purpose to reduce lift by disturbing airflow.
Example Sentence 1
After the main wheels touched down, the spoilers deployed automatically and the airplane settled firmly onto the runway.
Example Sentence 2
After touchdown the crew raised the spoilers to dump lift and shorten the landing roll on the short runway.