A sexual act involving 3 people, at least 2 of whom are men, in which one person's mouth and anus are simultaneously penetrated by a penis which then fills each cavity with urine.
- Dude, we should totally go water ballooning tonight!
- Honey, thanks for that romantic dinner -- now let's get a third so you can water balloon me!
- Oy, what a night! I got hella water ballooned and am totally wrecked today.