Plain English Meaning
A tight turn flown while the airplane is gliding (no engine power), usually at a steep bank, to change direction fast without losing more height or speed than necessary.
Full Definition
A steep turn performed without engine power, typically at a bank angle of around 45 degrees, used to reverse direction quickly while maintaining best glide airspeed during an engine-out scenario such as a takeoff failure with sufficient altitude to attempt a return to the runway.
Context Anchor
Encountered in training for engine failure shortly after takeoff, especially when discussing the danger of trying to turn back to the runway at low altitude.