Source : Webster's Revised Unabridged Dictionary (1913)

Gnarly \Gnarl"y\, a.
   Full of knots; knotty; twisted; crossgrained.

Source : WordNet®

gnarly
     adj : used of old persons or old trees; covered with knobs or
           knots; "gnarled and knotted hands"; "a knobbed stick"
           [syn: {gnarled}, {knotted}, {knotty}, {knobbed}]

Source : Free On-Line Dictionary of Computing

gnarly
     
         /nar'lee/ Both obscure and {hairy}.  "{Yow}! - the
        tuned {assembler} implementation of {BitBlt} is really
        gnarly!"  From a similar but less specific usage in surfer
        slang.
     
        [{Jargon File}]
     
        (1996-09-17)