Plain English Meaning
It's the spot where the wind is pushing you from behind, so you're moving across the ground faster than at any other point.
Full Definition
The point during a ground reference maneuver or traffic pattern leg where the airplane is flying with the wind directly behind it, producing the highest groundspeed of the maneuver.
Context Anchor
Seen in ground-reference maneuvers and constant-radius turning flight, where the pilot must adjust the turn to keep the airplane on the intended path over the ground.