A variation on the classic Icy Mike but with a festive "twist". (1) deposit feces on celophane. Ideally, one would want a fairly firm log-shaped crap (2) add semenal fluid (liberally) to feces for somewhat of a marbled affect (3) wrap entire piece up (while maintaining or creating log shape) (4) freeze (5) use to fuck, when appropriate.
My girlfriend Julia loved the Icy Mike so much, that I decided to step it up a notch and surprise her with a Jack Frost for the holidays.
Alright kids, a jack nasty is where a boy usually high school or younger who can't get laid masturbates 'jacks off' into some tissues. Since he is often not one to properly discpose of them, they drift about the room and eventually make their residence beneath his bed.
The resulting hard, crusty tissue wad peeking out from beneath the mattress... Is a jack nasty.