A fat man's hairy ass. The Swamp is usually not washed for days and therefore has a "swampy" reference when described. depending on how long it has been since the fat man has washed his swamp, there may be forms of life adapting to their new "swampy" environment. One does not have to neccesarily be fat to adapt a swamp, but the extra fat and ass space will allow for more wilderness to grow upon ones anal environment. Caution: the swamp may become thicker and much harder to navigate as one becomes closer to the anal cavity or around the Gooch area.
damn, that guy in front of us has swamp-ass. i can practically see the fumes.