This is the female ('human') version of 'gnarly'. A pathetic girl whom is physically dirty/greasy. She can be a TRY HARD whom pretends a lot. Also tends to be ignorant to the fact they are in all ways - repulsive. Other describing words would include fake, poser, annoying, lazy and filthy.
A particular individual who lives a radical, dangerous, and always extreme lifestyle. Often caught demonstrating his surf stance in everyday situations. Also always appears to be under the influence of some sort of drug.
"that gnarhead head drank 3 four lokos and took 2 hits of acid! Now he's trying to bomb parking garages on his long board"
"Has anyone seen the Chris?"
"Yeah, that gnarhead has been staring at the lava lamp for 2 hours."
Famous gnarheads:
Steve-o (Jackass/Wildboyz)
Chicken Joe (Surf's Up)
Jeff Bridges (The Big Lebowski)
Slater (Dazed and Confused)
Otto Rocket (Rocket power)
Keanu Reeves (Always)