Source : Webster's Revised Unabridged Dictionary (1913)

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}.]
   1. A fabulous serpent whose breath and look were said to be
      fatal. See {Basilisk}.

            That bare vowel, I, shall poison more Than the
            death-darting eye of cockatrice.      --Shak.

   2. (Her.) A representation of this serpent. It has the head,
      wings, and legs of a bird, and tail of a serpent.

   3. (Script.) A venomous serpent which which cannot now be
      identified.

            The weaned child shall put his hand on the
            cockatrice's

   Note: [Rev. Ver. basilisk's] den.              --Is. xi. 8.

   4. Any venomous or deadly thing.

            This little cockatrice of a king.     --Bacon.

Source : WordNet®

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