Plain English Meaning
Using the controls together in the right amounts so the airplane turns and maneuvers cleanly, without sliding sideways.
Full Definition
The simultaneous and balanced use of the flight controls — ailerons, elevator, and rudder — so the airplane responds smoothly and flies without slipping or skidding through the air.
Context Anchor
You will meet this term when learning basic airplane control, turns, climbs, descents, and any maneuver where more than one control is used at the same time.