Definition
Panels on the upper surface of the wing that deploy after touchdown to destroy lift and increase drag, transferring the airplane's weight onto the landing gear so wheel braking becomes more effective and the landing roll is shortened.
Plain English
Flat panels on top of the wing that pop up the moment the airplane lands. They kill the wing's lift so the airplane settles firmly onto its wheels, and they add drag to help slow the airplane down. Both effects help the brakes work better and stop the airplane in a shorter distance.
Context Anchor
Seen in landing, rejected takeoff, and drag-device discussions, especially on larger or higher-performance airplanes.
Derivation
Spoiler' comes from the idea of 'spoiling' the smooth airflow over the wing. 'Ground' is added because these panels are designed to be used only on the ground, not in flight. The name tells you what they do (spoil lift) and when they do it (on the ground).
Why Pilots Care
Shortens landing distance and improves directional control, especially on wet or short runways.
Grounding Statement
After touchdown, picture panels rising from the wing so the airplane stops trying to fly and presses more firmly onto the runway.
Intuition Check
Ground spoilers are not objects on the ground, and they are not “spoilers” in the everyday sense of ruining a surprise. “Ground” means they are used when the airplane is on the runway, and “spoilers” means panels that disrupt lift.
Example Sentence 1
After touchdown, the ground spoilers deployed automatically and the captain felt the airplane settle firmly onto the gear before applying the brakes.
Example Sentence 2
On a contaminated runway the crew relied on ground spoilers to keep the airplane firmly planted during deceleration.