When a sexual partner inserts a balloon into the cavity of their receptive partner and expels air to inflate the balloon inside the cavity, usually the anus.
When you blow into a woman’s vagina and fill up her gut with air making it almost look like a small balloon is in her gut.
Guy 1: hey bro guess what I did to my girlfriend last night
Guy 2: what’d you do?
Guy 1: we did some ballooning dude, she looked pregnant after the 3rd time.
An act performed whilst masturbating, when an uncircumcised male pinches his foreskin just before ejaculation, trapping the semen in his hood. Then later disposing it in the toilet.