Definition
Cockpit controls, usually shaped as small rotating wheels, used by the pilot to adjust the airplane's trim system so that the aircraft maintains a desired flight attitude without the pilot needing to hold continuous pressure on the flight controls. The most common is the elevator (pitch) trim wheel; some aircraft also have rudder and aileron trim wheels.
Plain English
Small wheels in the cockpit that the pilot turns to relieve the steady pressure they would otherwise have to hold on the yoke or rudder pedals. Once trimmed, the airplane stays in the chosen attitude on its own.
Context Anchor
Seen during cockpit preflight checks, before takeoff setup, and anytime the pilot adjusts trim in flight.
Derivation
From the nautical term 'trim,' meaning to adjust a vessel's balance. In aviation, trimming likewise means balancing the aircraft so it flies steadily without constant pilot input.
Why Pilots Care
Proper trim reduces control pressure, lowers pilot workload, prevents fatigue on longer flights, and lets the aircraft maintain altitude and heading more precisely with less input.
Intuition Check
Do not read trim here as decoration or cutting something shorter. In this context, trim means a small adjustment that helps the airplane stay balanced with less hand pressure.
Example Sentence 1
After leveling off at cruise altitude, the pilot rolled the elevator trim wheel forward until the control yoke felt neutral.
Example Sentence 2
After leveling off in cruise, the pilot turned the trim wheels forward a few clicks to remove the back pressure needed to hold altitude.