1. An exclamation used to describe something which is awe-inspiring, usually of something generally deemed to be "twisted"; most often said in a manner mocking of the speech typically associated with mentally retarded individuals.
The deepest of the deep. The driest of the dry. The powest of the pow pow. It's the powda baby!
Snowboarder: Duuuude, check the dump bra. Lets go shred the gnar gnar!
Skier: Good day ole chap, have you seen the weather report? By jove there was a biblical blizzard this night past. Shall we shred the gnar?