Plain English Meaning

Something has gone wrong with the parts of the airplane that let the pilot steer it. A control might be stuck, broken, disconnected, or only working part way, so the airplane doesn't respond normally to stick, yoke, rudder pedal, or trim inputs.

Full Definition

A condition in which one or more of the airplane's primary or secondary flight controls fails to operate normally, operates only partially, jams, disconnects, or responds incorrectly to pilot input. This includes problems with the ailerons, elevator, rudder, trim systems, flaps, or the cables, pushrods, hydraulic actuators, and electrical systems that move them.