Plain English Meaning
During the VMC demo, the pilot eases off the rudder on purpose so the airplane starts to yaw, which shows the loss of control point safely instead of flying it all the way down to the real limit.
Full Definition
A method used during a VMC demonstration in a multi-engine airplane in which the pilot deliberately reduces rudder input before full rudder is reached, allowing the airplane to begin yawing toward the inoperative engine. This induced loss of directional control simulates VMC at a safer altitude and airspeed margin than waiting for actual aerodynamic rudder limits, and it provides the recovery cue without requiring an approach to stall.