Cockatrice

n.
  1. A fabulous serpent whose breath and look were said to be fatal. See Basilisk.
  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.
  4. Any venomous or deadly thing.

[Rev. Ver. basilisk's]