when you jump and crap at the same time.
Guy 1:Oh my god, you see that guy over there??
Guy 2: yeah... why?
Guy 1: HE JUST DID A JUMP-A-DUMP!!!
Guy 2: damn!
When you get hit in the bottom of your scrotum, like getting uppercutted but for your nuts.
Girl: You ok?
Guy: No. I dropped my phone and I nuppercutted myself