The act of after a physical sporting event (football, lacrosse, etc.) taking your protective cup out of its jock strap and creeping up behind an unsuspecting teammate and placing it forcefully over their nasal passages and mouth. Immediatly after doing so, the victim is tackled to the ground and the cup will be held on for as long as possible until the victim fights himself off from the grapple.
Post attack, the victim is especially angry and considered extremely dangerous. Keep distance and seek shelter.
Maximum effect achieved on a hot, humid day after a long practice, in which the cup will reek of a putrid smell and be oddly moist.
Paco gave me The Cupface after lax let out yesterday. It was the worst thing I've ever seen in my life.