Plain English Meaning
A controlled maneuver where the airplane flies slightly sideways through the air, with one wing lowered and the nose held off to the opposite side using the rudder.
Full Definition
A flight condition in which the airplane's longitudinal axis is not aligned with the relative wind, causing the aircraft to move partly sideways through the air. In a sideslip, the aircraft's heading and flight path differ, with the nose pointed away from the direction of travel. It is intentionally produced by applying opposite aileron and rudder, so that the bank in one direction is balanced by yaw in the other.
Context Anchor
Seen in discussions of uncoordinated flight, and , and .