the act of holding your foreskin closed while urinating so it fills up like a water balloon
Jake: Hey David what are you doing tonight?
David: Nothing probably just going to sit in the shower and do some water ballooning
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.
the practice of urination in ones partner whilst wearing a condom
"honey we are going to have to stop, one needs a slash"
"that's ok honey you can keep water ballooning me"