(1):

(n.) A venomous serpent which which cannot now be identified.

(2):

(n.) Any venomous or deadly thing.

(3):

(n.) A fabulous serpent whose breath and look were said to be fatal. See Basilisk.

(4):

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