Webster's Revised Unabridged Dictionary · 1913

Cockatrice

Cockatrice (-trīs; 277) , noun

[Old French cocatrice crocodile, French cocatrix, cocatrice. The word is a corruption from the same source as English crocodile, but was confused with cock the bird, French 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. — Shakespeare
2.
(Heraldry) A representation of this serpent. It has the head, wings, and legs of a bird, and tail of a serpent.
3.
(Scripture) A venomous serpent which which cannot now be identified.
The weaned child shall put his hand on the cockatrice's [Rev. Ver. basilisk's] den. — Is. xi. 8

[Rev. Ver. basilisk's]

4.
Any venomous or deadly thing.
This little cockatrice of a king. — Bacon