The act of rolling a nipple in between your thumb and pointer fingers until it achieves hardness, then flick the hardend nipple.
Guy1: Dude, her nips were hard enough to boogernipple them!
Guy2: What do you mean?
Guy1: You know how you pick your nose and roll the booger into a ball and then flick it once it's hard?
Guy2: Yea.
Guy1: That's how hard they were!