Meaning of trim tab

trim' tab"

Pronunciation: [key]
— Aeron. Aeron.
  1. an independently controlled tab set in the trailing edge of a control surface, as an elevator, aileron, or rudder, to hold it in a position suitable for stabilizing the aircraft in a flight attitude.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.