The Collaborative International Dictionary of English v.0.48:

Serpent \Ser"pent\, n. [F., fr. L. serpens, -entis (sc. bestia),
   fr. serpens, p. pr. of serpere to creep; akin to Gr. ???,
   Skr. sarp, and perhaps to L. repere, E. reptile. Cf.
   Herpes.]
   1. (Zool.) Any reptile of the order Ophidia; a snake,
      especially a large snake. See Illust. under Ophidia.
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   Note: The serpents are mostly long and slender, and move
         partly by bending the body into undulations or folds
         and pressing them against objects, and partly by using
         the free edges of their ventral scales to cling to
         rough surfaces. Many species glide swiftly over the
         ground, some burrow in the earth, others live in trees.
         A few are entirely aquatic, and swim rapidly. See
         Ophidia, and Fang.
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   2. Fig.: A subtle, treacherous, malicious person.
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   3. A species of firework having a serpentine motion as it
      passess through the air or along the ground.
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   4. (Astron.) The constellation Serpens.
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   5. (Mus.) A bass wind instrument, of a loud and coarse tone,
      formerly much used in military bands, and sometimes
      introduced into the orchestra; -- so called from its form.
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   Pharaoh's serpent (Chem.), mercuric sulphocyanate, a
      combustible white substance which in burning gives off a
      poisonous vapor and leaves a peculiar brown voluminous
      residue which is expelled in a serpentine from. It is
      employed as a scientific toy.

   Serpent cucumber (Bot.), the long, slender, serpentine
      fruit of the cucurbitaceous plant Trichosanthes
      colubrina; also, the plant itself.

   Serpent eage (Zool.), any one of several species of
      raptorial birds of the genera Circaetus and Spilornis,
      which prey on serpents. They inhabit Africa, Southern
      Europe, and India. The European serpent eagle is
      Circaetus Gallicus.

   Serpent eater. (Zool.)
      (a) The secretary bird.
      (b) An Asiatic antelope; the markhoor.

   Serpent fish (Zool.), a fish (Cepola rubescens) with a
      long, thin, compressed body, and a band of red running
      lengthwise.

   Serpent star (Zool.), an ophiuran; a brittle star.

   Serpent's tongue (Paleon.), the fossil tooth of a shark; --
      so called from its resemblance to a tongue with its root.


   Serpent withe (Bot.), a West Indian climbing plant
      (Aristolochia odoratissima).

   Tree serpent (Zool.), any species of African serpents
      belonging to the family Dendrophidae.
      [1913 Webster]

WordNet (r) 3.0 (2006):

serpent star
    n 1: an animal resembling a starfish with fragile whiplike arms
         radiating from a small central disc [syn: brittle star,
         brittle-star, serpent star]