butt popping 

The sound a dick makes upon exiting the anus.

I heard him butt popping her from the other room.

butt popping by andys mom July 18, 2016

Popping your butt knuckle 

Farting or getting raped in the ass by a large shemale.

Dude that one website you sent me to last night was digusting, I didn't know shemales could be Popping your butt knuckle.

Popping your butt knuckle by UF Omega September 13, 2011