naked handshake
When two guys who are either completely naked or just showing off their junk greet each other by pulling each other's dongs like they're in a cock fight.
At the nudist club, the two guys did a naked handshake and then walked into the hot tub.
In the middle of the work break, the two coworkers did a naked handshake and laughed like they were kids again.
At the park, the two guys did a naked handshake and then played a game of chess with their bare butts.