Plain English Meaning
Using the rudder pedals and the control wheel together so the airplane turns smoothly, with the nose tracking properly through the turn instead of sliding sideways.
Full Definition
The simultaneous, balanced use of rudder and ailerons during a turn so that the airplane rolls and yaws together, keeping the longitudinal axis aligned with the flight path and preventing slipping or skidding. When the ailerons are deflected to bank the airplane, the rudder is applied in the same direction and in the right amount to counter adverse yaw and maintain coordinated flight.
Context Anchor
Encountered during steep-turn training, especially while into the turn, a steady bank, and on the desired .