nasty, gnarley, disgusting, pretty much anything you wouldnt wanna touch/eat/smell/look at.
"damn..this ham is gnars"
"damn..your mom is gnars"
girl: ohmahhgawd that guy is soo hott
other girl: i dunno, he looks pretty gnars to me.
Something that is extremely disgusting. Something that is so utterly repulsive that the very site of it induces vomit.
Can be used to discribe a person or thing.
John: Dude, want some of this pizza?
Dave: Dude no its a week old. Thats so gnars.