A fat chick or a fatty posse. Derived from the fat girl sorority Omega Mu in the movie Revenge of the Nerds. The Omega Mu plumpers help the nerds such as Takashi, Wormser, Poindexter, Lewis and Gilbert, Lamar Latrell and Booger combat the jocks and cheerleaders and they put on a concert and take control of the campus.
"Look at that big fat fatty in the short skirt and tight, low cut top!"
"What an Omega Mu!"