When you succeed putting your unerrected cock into an unconsented hobo's asshole and then you get an erection inside him.
Eric: Dude, I gave a Dirty Boner to a hobo last night.
Guillaume: Did you wash your cock?
Eric: No. I like it better with this human nutella on it.
Guillaume: You're so funny. Wanna fuck?
Eric: Awesome dude!