The Collaborative International Dictionary of English v.0.48:

Gnarl \Gnarl\, v. i. [imp. & p. p. Gnarled; p. pr. & vb. n.
   Gnarling.] [From older gnar, prob. of imitative origin; cf.
   G. knarren, knurren. D. knorren, Sw. knorra, Dan. knurre.]
   To growl; to snarl.
   [1913 Webster]

         And wolves are gnarling who shall gnaw thee first.
                                                  --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gnarled \Gnarled\, a.
   Knotty; full of knots or gnarls; twisted; crossgrained.
   [1913 Webster]

         The unwedgeable and gnarl['e]d oak.      --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

gnarled
    adj 1: used of old persons or old trees; covered with knobs or
           knots; "gnarled and knotted hands"; "a knobbed stick"
           [syn: gnarled, gnarly, knotted, knotty,
           knobbed]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "gnarled":
   arthritic, bent, bumpy, burled, contorted, crooked, distorted,
   gnarly, knobbed, knobbly, knobby, knoblike, knotted, knotty,
   knurled, knurly, lumpy, nodal, noded, nodiform, nodose, nodular,
   nodulated, noduled, nubbled, nubbly, nubby, studded, torose,
   tubercular, tuberculous, tuberose, tuberous, twisted, warped