Gnar Juice is something you drink (or smoke) to get you super pumped and ready to get gnarly. It can be anything like water, Beer, Red Bull, even sweet Mary Jane.
Mike: "You ready to skate this big rail?"
Scott: "Hell yeah man, I just smoked some gnar juice."

Jeff: "Hey could you grab my jug of Gnar Juice out of the fridge?"

by Scotty Karate November 15, 2005
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