In the gay community, boba is an acronym standing for "bum on bum action." This action involves one person touching the others' bum with their own bum. Not to be confused with "incidental boba" when a man sits on the same toilet seat after another man has already used it.
Rob: Hey Marty, you ready for some boba?
Marty: Fo sho.
A: Don't touch my ass with your ass; I don't want any boba today.