This is horrible abuse to do to a person. You rub your knuckle against either your own, your victim's, or a third parties butthole then proceed to rub your "dirty knuckle" against your victim's mouth.
Tiffany: "Danny, if you don't stop making fun of my nips, I'm gonna give you the dirty knuckler!"
Danny: "NAY!"
Danny: "NAY!"
by thecottoncandypinkprincess September 29, 2011