1. (v) The act of removing the contents of someone's backpack, turning it inside out, and re-inserting the contents into the inside out bag, usually during class.
2. (n) The victorious exclamation often proclaimed after a successful Punk Nasty.
3. (var) Funk (or Dunk/Chunk) Nasty: A variation on the Punk Nasty in which the assailant uses the Punk Nastied backpack as a fecal receptacle (ie takes a shit inside it).

To punk nasty someone is to take their backpack, remove the contents, turn the backpack inside-out, replace the contents, and then zip it back up. To double punk nasty a pair of people, one punk nastys each person, but swaps the contents of their packs.