(1):

(n.) A large piece of ordnance, so called from its supposed resemblance to the serpent of that name, or from its size.

(2):

(n.) A fabulous serpent, or dragon. The ancients alleged that its hissing would drive away all other serpents, and that its breath, and even its look, was fatal. See Cockatrice.

(3):

(n.) A lizard of the genus Basiliscus, belonging to the family Iguanidae.