To be beat badly at an event. Derived from the all-pro nfl star Randy Moss and his historic 2007 campaign. Normally used to say that you destroyed someone else in a competition. Kind of like saying pwned.
Commentator: And the final score is, Redskins, 37, Cowboys, 10.
Redskins fan: HAHA! MOSSED! SUCK IT BITCH!
Cowboys fan: Sigh....