the act in which one person inserts an object into the poop chute of another. similar to fisting. one usually screams "up the butt johnson!!!" when performing an up the butt johnson. best used when the receiver doesn't see it coming. stealth greaty enhances the experience of an up the butt johnson.
PERSON A: (while giving PERSON B an up the butt johnson) "UP THE BUTT JOHNSON!!!!!"
PERSON B: ah what the hell man! that hurts my crack!
PERSON A: lol! i just thrusted my phone in your ass!