(n.)- A diagram illustrating how people in a certain institution (especially a school or small college) are all connected with an interconnecting web of who's hugged/kissed/dated/made out/made love/had buttsex/etc. with who. In order to be included in a poop circle, you must have had more than one of the kinds of the relations listed (and having them with the same person doesn't count). The resulting picture, if done correctly, looks like crap, but is very revealing.
Guy #1: "Hey man, I drew a poop circle that has all of the girls in our grade! Look at Kesha
(points to the symbol "KS" in the drawing and all of its branches)
Guy #2: "Whoa, she was in a threesome
? AND she did it with that nerd Steve Urkel
? Oh, she's loose; I'll ask her to prom!"