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.
A: What's with the tissues, dude?
A: Man you was makin' jack nasties!
Man that chick was so fine but I'll never
get with her. I cry alone at night and make jack nasties.