bag pooper
A person who poops in a bag. The bag can be paper or plastic. Anyone who takes a dump in a bag.
J: "oh shit, I can't find a fuckin toilet!" Hey, I guess I could take a dump in this newspaper rain bag.....
(Takes a dump in the bag)
B: I guess that makes you a bag pooper!
(Takes a dump in the bag)
B: I guess that makes you a bag pooper!