A gay sex act which involves but is not limited to entering a shower, bathtub, or sauna for the purpose of contracting multiple sexually transmitted infections such as gonorrhea, herpes, and genital warts. Quite often bubble bath or conditioner is used as lubrication to penetrate the anus. This often leaves both participants feeling dirtier than when they entered.
Jole: Did you hear that Bret gave Frank a bumpy shower?
Matt: Yea man, I heard they're both burnin now
or
Jole: I've been farting bubbles all day man what happened last night?
Matt: You don't remember? We took a bumpy shower.