The Collaborative International Dictionary of English v.0.48:

Serpentine \Ser"pen*tine\, n. [Cf. (for sense 1) F. serpentine,
   (for sense 2) serpentin.]
   1. (Min.) A mineral or rock consisting chiefly of the hydrous
      silicate of magnesia. It is usually of an obscure green
      color, often with a spotted or mottled appearance
      resembling a serpent's skin. Precious, or noble,
      serpentine is translucent and of a rich oil-green color.
      [1913 Webster]

   Note: Serpentine has been largely produced by the alteration
         of other minerals, especially of chrysolite.
         [1913 Webster]

   2. (Ordnance) A kind of ancient cannon.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Serpentine \Ser"pen*tine\, a. [L. serpentinus: cf. F.
   serpentin.]
   Resembling a serpent; having the shape or qualities of a
   serpent; subtle; winding or turning one way and the other,
   like a moving serpent; anfractuous; meandering; sinuous;
   zigzag; as, serpentine braid.
   [1913 Webster]

         Thy shape
         Like his, and color serpentine.          --Milton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Serpentine \Ser"pen*tine\, v. i.
   To serpentize. [R.] --Lyttleton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

serpentine
    adj 1: resembling a serpent in form; "a serpentine wall"; "snaky
           ridges in the sand" [syn: serpentine, snaky,
           snakelike]

Moby Thesaurus II by Grady Ward, 1.0:

223 Moby Thesaurus words for "serpentine":
   Byzantine, Machiavellian, Machiavellic, Mephistophelian, aberrant,
   aberrative, acute, affluent, ambagious, amphibian, anfractuous,
   anguiform, anguine, arch, artful, astute, bad, batrachian, bent,
   billowing, billowy, cagey, canny, circuitous, circumlocutory,
   clever, colubriform, complex, complicated, confluent, conniving,
   convoluted, convolutional, coursing, crafty, crawling, creeping,
   crocodilian, crooked, cunning, curvaceous, curvate, curvated,
   curve, curved, curvesome, curviform, curvilineal, curvilinear,
   curving, curvy, cute, deceitful, decurrent, deep, deep-laid,
   defluent, demoniac, demonic, departing, designing, desultory,
   deviant, deviating, deviative, deviatory, devilish, devious,
   diabolic, diabolical, diffluent, digressive, diplomatic,
   discursive, eellike, errant, erratic, evil, excursive, feline,
   flexuose, flexuous, flowing, fluent, fluxional, fluxive, foxy,
   froggy, geosynclinal, guileful, gulfy, gushing, incurvate,
   incurvated, incurved, incurving, indented, indirect, ingenious,
   insidious, inventive, involute, involuted, involutional, knowing,
   labyrinthine, lizardlike, lumbriciform, mazy, meandering,
   meandrous, notched, ophidian, out-of-the-way, pawky, planetary,
   plotting, politic, pouring, profluent, racing, rambling, ready,
   recurvate, recurvated, recurved, recurving, repent, reptant,
   reptile, reptilelike, reptilian, reptiliform, reptiloid,
   resourceful, rivose, rivulose, roundabout, roving, ruffled,
   running, rushing, satanic, saurian, saw-toothed, sawtooth,
   scheming, scored, serpentiform, serpentile, serpentlike,
   serpentoid, serrate, serrated, serried, sharp, shifting, shifty,
   shrewd, sinuate, sinuose, sinuous, slick, slippery, slithering,
   sluggish, sly, smooth, snake-shaped, snakelike, snaking, snaky,
   sneaky, sophistical, stealthy, strategic, stray, streaming,
   subtile, subtle, supple, surging, surgy, swerving, tactical, tidal,
   toadish, toothed, torsional, tortile, tortuous, trickish, tricksy,
   tricky, turning, twisting, twisty, undirected, undulant,
   unhallowed, vagrant, veering, vermicular, vermiculate, vermiform,
   viperiform, viperish, viperlike, viperoid, viperous, vipery,
   vortical, vulpine, wandering, wary, wavy, whorled, wily, winding,
   wormlike, wreathlike, wreathy, zigzag