youbetchurass
Colloquialization of "You bet your ass" indicating that said event is so sure to occur that you can safely bet your own ass on the matter without worry. This is meant as a metaphor and implies no prejudice concerning the actual weight of said ass.
"Dude that chicks done nothing but stare at you all night. "You gonna ask her out?"
"Youbetchurass!"
"Youbetchurass!"