Plain English Meaning

Resetting the trim again because something has changed and the airplane is no longer flying hands-off the way it was before.

Full Definition

The act of readjusting the airplane's trim controls to relieve sustained control pressure after a change in airspeed, power setting, configuration, or attitude has altered the previously trimmed condition.

Context Anchor

Used during climbs, descents, level-offs, power changes, flap changes, and any time the airplane no longer feels balanced in the pilot’s hands.

Derivation

The prefix 're-' means 'again.' 'Trim' in refers to small adjustable surfaces (or ) that a input for the pilot so the airplane flies steady without the pilot having to hold on the or . So 're-trimming' literally means again — repeating the adjustment after have changed.