NOUN (3)

1. (classical mythology) a serpent (or lizard or dragon) able to kill with its breath or glance;

2. ancient brass cannon;

3. small crested arboreal lizard able to run on its hind legs; of tropical America;

The Collaborative International Dictionary of English v.0.48:

Basilisk \Bas"i*lisk\, n. [L. basiliscus, Gr. basili`skos little
   king, kind of serpent, dim. of basiley`s king; -- so named
   from some prominences on the head resembling a crown.]
   1. 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.
      [1913 Webster]

            Make me not sighted like the basilisk. --Shak.
      [1913 Webster]

   2. (Zool.) A lizard of the genus Basiliscus, belonging to
      the family Iguanid[ae].
      [1913 Webster]

   Note: This genus is remarkable for a membranous bag rising
         above the occiput, which can be filled with air at
         pleasure; also for an elevated crest along the back,
         that can be raised or depressed at will.
         [1913 Webster]

   3. (Mil.) A large piece of ordnance, so called from its
      supposed resemblance to the serpent of that name, or from
      its size. [Obs.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

basilisk
    n 1: (classical mythology) a serpent (or lizard or dragon) able
         to kill with its breath or glance
    2: ancient brass cannon
    3: small crested arboreal lizard able to run on its hind legs;
       of tropical America

Easton's 1897 Bible Dictionary:

Basilisk
   (in R.V., Isa. 11:8; 14:29; 59:5; Jer. 8:17), the "king
   serpent," as the name imports; a fabulous serpent said to be
   three spans long, with a spot on its head like a crown. Probably
   the yellow snake is intended. (See COCKATRICE.)


The Devil's Dictionary (1881-1906):

BASILISK, n.  The cockatrice.  A sort of serpent hatched form the egg
of a cock.  The basilisk had a bad eye, and its glance was fatal.
Many infidels deny this creature's existence, but Semprello Aurator
saw and handled one that had been blinded by lightning as a punishment
for having fatally gazed on a lady of rank whom Jupiter loved.  Juno
afterward restored the reptile's sight and hid it in a cave.  Nothing
is so well attested by the ancients as the existence of the basilisk,
but the cocks have stopped laying.