To get it on with someone in the bathroom, most likely a club or bar. Usually those involved are either really drunk or just a ho.
Dude1:Man that girl over there is looking at you man, she lookin a lil tipsy too.
Dude2:Yea, I think she might be that kinda girl that is a candidate for a bathroom bop.
Dude:hey babe, you lookin good, ya wanna go to the bathroom and jump in a stall.
Chcik:Ah hell no! I aint no bathroom bop