第五教 · Dai Gokyo
Ushiro Goshi 後腰
Rear Hip
Mechanic
As uke turns in for a hip throw, tori sinks low behind them, hugs their waist, and heaves them straight up off the floor on tori's hips, then tilts and pulls the platform away so uke drops flat onto their back.
Analogy
You are sitting on the back of a hay wagon when it bangs through a pothole. The whole bed heaves up and launches you straight into the air. Then the wagon rolls on out from underneath, and there is nothing left to come down onto but the road.
Why it maps
The wagon bed is tori's hips: it throws you vertically off the ground and then moves out from under you, so you land flat on your back with nothing to catch you.