adj. Incredibly sick and twisted. Disgustingly mind-bending. Used outside of extreme sports to describe a bass-line or grouping of psychedelic sounds as heard in drum n' bass, dubstep, and many other genres of electronic music, hip-hop, and rock. Can also refer to visual art that is ground-breaking or brain-shattering, especially in the realm of graffiti and tagging.
Junglist: "Holy shit did you hear that bass-line? How the hell did they do that?! Shit is fucking gnar gnar!"
Head: "Have you seen that burner on 200 south? It's gnar gnar as fuck!"