Acronym for "up your butt with a coconut"
It sounds kind of stupid when you say it to someone, mostly because they usually don't know what you're talking about and probably think that you're a retard. Once you explain what it means you'll probably get your ass kicked.
Bob - "Uybwac, and wyai (while you're at it) you can gfym (go fuck your mother) yddb (you dirty dooshbag)!"
Johnson - "Igbyamf (I'm gonna beat yo' ass beotch)!"