Definition
To readjust the aircraft's trim controls to relieve control pressures after a change in airspeed, power setting, configuration, or attitude, so the aircraft maintains the new desired flight condition without continuous pilot input on the controls.
Plain English
To reset the trim wheel or trim controls so the aircraft holds the new attitude on its own, without the pilot having to keep pushing or pulling on the yoke.
Context Anchor
Used during instrument flying when changing power, leveling off, changing speed, or returning to straight-and-level flight.
Derivation
The prefix 're-' means 'again.' So 'retrim' literally means 'to trim again' — adjusting the trim a second (or further) time after the initial trim setting no longer holds the aircraft steady.
Why Pilots Care
Reduces pilot workload and prevents fatigue by eliminating the need for constant control pressure.
Intuition Check
Do not think of retrim as flying the airplane for you. First set the attitude and power you want, then retrim to remove the leftover control pressure.
Example Sentence 1
After reducing power for the descent, the pilot retrimmed to relieve the forward pressure on the yoke.
Example Sentence 2
Once established in level flight on the new heading, the instructor reminded the student to retrim before continuing the instrument scan.