Gnar to an obscene extent, ie.
1. One of the coolest things you've ever seen.
2. One of the most disgusting things you've ever seen.
3. In describing surf/snowboard/skate terrain/conditions, incredibly good.
1. Bro, did you see that Maserati? Hefty gnar.
2. This fat chick was puking everywhere at that party, so hefty gnar.
3. We just got back from a dope session at Lower Trestles, surf was hefty gnar!