Female version` of "Tea Bagging". The act of a female rubbing her genetalia on a mans head, face or body.
That stripper Felicia just fish tailed that guy.
Similar to a wedgie. The perpetrator sneaks up behind the victim and quickly inserts his fingers in between the victims ass cheeks, hitting the sensitive skin and putting tension on the victims cheeks and anus. If done correctly can be extremely painful, however should only be done in a joking manner among friends.
Mike: Damn I was walking in my living room yesterday, and Dana fucking fishtailed me so fucking hard.
Dave: Damn, that sucks dude. I hate Fishtailing
When girls who go to a uniform school roll their kilts wrong, the pleats at the back stick out.
Tawny: Man I was talking to Pete yesterday then I went to the bathroom and noticed I was fishtailing!
Olga: How embarrassing!