To take a huge crap. It may happen more than once a day. It is so big that you lose feeling in your legs and you think that your abdomen has imploded.
In reference to the South Park episode "More Crap" in which Randy Marsh takes the world's largest crap.
Guy 1: Are you okay?
Guy 2: Yeah, I just made a Randy Marsh upstairs.
Guy 1: Wow, did you run out of toilet paper? It must have been huge.
Guy 2. It was. It was a Randy Marsh.