Plain English Meaning
Moving the controls gently and steadily rather than sharply or in sudden bursts, so the airplane changes attitude in a smooth, controlled way.
Full Definition
The application of flight control inputs (aileron, elevator, and rudder) in a gradual, coordinated, and unhurried manner, avoiding abrupt or jerky movements so that the airplane responds predictably and the desired flight path is achieved without overcontrolling.
Context Anchor
Seen during maneuver practice such as steep turns, where the pilot must roll into the turn, hold the airplane steady, and return to without rough movements.