When you hold your foreskin closed so the end of your penis fills with urine.
I just did a huge welsh waterballoon in the shower
The act of urinating in someone’s asshole during anal sex.
“Holy shit dude, did you hear jonah tried waterballooning his girlfriend last night? Can’t believe he was able to piss with a boner.”
Verb;
When a male pulls his foreskin over the head of his penis, and ejaculates inside his foreskin. Then releasing it inside the mouth of a female.
I have my girl a Neapolitan Waterballoon last night. Just a big load of cum, sweat and tears. I don’t think she will let me surprise her like that again.