Definition
An electric motor that drives the trim system to adjust a flight control surface (such as the trim tab or, in some aircraft, the entire stabilizer) so the pilot does not have to hold continuous pressure on the controls. It is activated by a switch on the yoke or control stick, or by the autopilot.
Plain English
A small electric motor that moves a control surface a tiny bit so the airplane will fly hands-off at the speed and attitude the pilot wants.
Context Anchor
Seen in electric pitch-trim systems and adjustable-stabilizer systems, especially when setting takeoff trim or making small trim changes in flight.
Derivation
‘Trim’ comes from Old English ‘trymman’ meaning to make ready or set in proper order — the same sense used in sailing, where you ‘trim’ the sails to balance the boat. A trim motor is the electric device that does that balancing work for you.
Why Pilots Care
It reduces pilot fatigue by allowing stable flight without continuous yoke or stick input.
Intuition Check
Trim does not mean cutting something here. In this context, trim means adjusting the airplane’s control balance so it takes less steady force to hold the desired flight position.
Example Sentence 1
After leveling off in cruise, the pilot used the trim motor to relieve the back-pressure on the yoke.
Example Sentence 2
During the preflight check the pilot verified that the trim motor responded to both the cockpit switch and the autopilot commands.