To bump one's peter against another man's peter. Not for sexual pleasure, but to find out if one of the two parties involved becomes aroused.
Guy 1: Hey Dude, have you ever done a peter bump?
Guy 2: Hell no, I'm not gay!
Guy 1: Well how do you know if you've never peter bumped?
To snort a small convenient amount of cocaine off the tip of a man's genetalia.
During the party, one of Joe's dads sneaked a guest into the pool house for a quick Peter Bump