Pooterbutt

An ass that is even flatter, and even more embarrassing than a poohbutt. The absolute worst type of butt to have, or to look at. It practically tilts inward.

Man A: “Look at that poohbutt!” Man B: “No, dude, that’s a pooterbutt right there.”
“Omg, Becky, would you call my complete lack of having any ass a ‘poohbutt’? Or is it a ‘pooterbutt’?”