When you do something to piss someone off
Yea he ate my burger, he's a Jackass!!!
Jackass - A man whoms't has been left with their anal cavity exploded in, and has proceeded to wonder around without flushing it out
HEY!! There's one of those slutty town drinkers. I bet she has a whopping jackass
Verb.
The act of being immature, stupid, or acting like a jackass.
"Dude. Your jackassness is showing"
Person who executes the dumbest actions with such proficiency, observers are frozen in awe and are unable to reproduce such actions without extensive practice or training.
Turning the the wrong way on to a "One Way" street, on the phone and cursing the folks who got it right. That's a Pro Jackass, you can't be that dumb without practice and dedication.