Could be shakin' booty to some music.
Or it could be a "booty-to-booty" battle if ya know what I mean.
The two booties have some contact like, bumpin, slamming, pressing and comparing each others booties together in a competitive way.
"Lets shake our booties"
"Wanna have some booty fun together?"
"You can't beat my booty"
"Lets compare our booties"