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.
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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.
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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]