When you are having sex with a woman and only one of her tits moves, like you see all the time in a porno.
I was nailing this woman wheel barrow style and she had a Porno Titty going on because only her left tit was moving.
When you are fucking a chick and only one of her boobs is moving, just like you would see when a chick is getting fucked in a porno.
I was fucking this chick missionary and only her left titty was moving, so I was watching her porno titty.