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!
by Gars du 10 July 24, 2009
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When you slather your dong in chocolate so that it is lubed better and your spouse agrees to do anal, but when you finish doing it with them, they turn around and turn out to be a guy.
"Oh man, last night was WICKED! I was all ready to go and he pulled a dirty-boner on me!!"
by FatherTy April 19, 2022
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