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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!
by Plastic bag poopin' mofo May 13, 2008