If yo man or woman got that mountable pushing cushion, it can be referred to as a beasty ass. This could be for two reasons the tushy makes you tear up the pure sexual titillation each time that trouser material tightens or the ass is truly untameable, when you be bashing that bottom button your duck diving everywhere to avoid the beautiful bouncy booty.

Beasty arse is also used in some part of the world.
Partner squats to look in lowest cupboard
You (mental straining not to pounce on them) "fuck that's a beasty ass"
by TheDimeofTime January 26, 2018
Get the beasty ass mug.