Plain English Meaning

It is the small horizontal wing at the tail of the airplane, but built so the whole surface can tilt up or down. By tilting it, the pilot adjusts the airplane's natural balance so it flies steady without having to hold pressure on the controls.

Full Definition

A horizontal stabilizer whose angle of incidence (the angle at which it meets the oncoming airflow) can be changed in flight by the pilot or the trim system, allowing the airplane to be trimmed for hands-off level flight across a wide range of , weights, and -of- .