The Collaborative International Dictionary of English v.0.48:

Cockatrice \Cock"a*trice\ (-tr[imac]s; 277), n. [OF. cocatrice
   crocodile, F. cocatrix, cocatrice. The word is a corruption
   from the same source as E. crocodile, but was confused with
   cock the bird, F. coq, whence arose the fable that the animal
   was produced from a cock's egg. See Crocodile.]
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   1. A fabulous serpent whose breath and look were said to be
      fatal. See Basilisk.
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            That bare vowel, I, shall poison more
            Than the death-darting eye of cockatrice. --Shak.
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   2. (Her.) A representation of this serpent. It has the head,
      wings, and legs of a bird, and tail of a serpent.
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   3. (Script.) A venomous serpent which which cannot now be
      identified.
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            The weaned child shall put his hand on the
            cockatrice's

   Note: [Rev. Ver. basilisk's] den.              --Is. xi. 8.
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   4. Any venomous or deadly thing.
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            This little cockatrice of a king.     --Bacon.
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WordNet (r) 3.0 (2006):

cockatrice
    n 1: monster hatched by a reptile from a cock's egg; able to
         kill with a glance