The Collaborative International Dictionary of English v.0.48:

Chameleon \Cha*me"le*on\ (k[.a]*m[=e]"l[-e]*[u^]n), n. [L.
   Chamaeleon, Gr. chamaile`wn, lit., "ground lion;" chamai` on
   the ground + le`wn lion. See Humble, and Lion.] (Zool.)
   1. A lizardlike reptile of the genus Cham[ae]leo, of
      several species, found in Africa, Asia, and Europe. The
      skin is covered with fine granulations; it has eyes which
      can move separately, the tail is prehensile, and the body
      is much compressed laterally, giving it a high back. It is
      remarkable for its ability to change the color of its skin
      to blend with its surroundings. [Also sometimes spelled
      chamaeleon.]
      [1913 Webster +PJC]

   Note: Its color changes more or less with the color of the
         objects about it, or with its temper when disturbed. In
         a cool, dark place it is nearly white, or grayish; on
         admitting the light, it changes to brown, bottle-green,
         or blood red, of various shades, and more or less
         mottled in arrangment. The American chameleons belong
         to Anolis and allied genera of the family
         Iguanid[ae]. They are more slender in form than the
         true chameleons, but have the same power of changing
         their colors.
         [1913 Webster]

   2. a person who changes opinions, ideas, or behavior to suit
      the prevailing social climate; an opportunist.
      [PJC]

   Chameleon mineral (Chem.), the compound called potassium
      permanganate, a dark violet, crystalline substance,
      KMnO4, which in formation passes through a peculiar
      succession of color from green to blue, purple, red, etc.
      See Potassium permanganate, under Potassium.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chameleon
    n 1: a changeable or inconstant person
    2: a faint constellation in the polar region of the southern
       hemisphere near Apus and Mensa [syn: Chamaeleon,
       Chameleon]
    3: lizard of Africa and Madagascar able to change skin color and
       having a projectile tongue [syn: chameleon, chamaeleon]

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "chameleon":
   April showers, Dalmatian, Gila monster, Proteus, Vicar of Bray,
   agama, alligator, anole, antigorite, bearded lizard, blindworm,
   box turtle, butterfly, butterfly agama, candy cane, cayman,
   cheetah, chrysotile, cloud shapes, confetti, crazy quilt,
   crocodile, diamondback, dragon, false map turtle, firedog,
   flying dragon, formalist, gavial, gecko, girdle-tailed lizard,
   glass snake, green turtle, harlequin, hawksbill, hawksbill turtle,
   iguana, iris, jaguar, kaleidoscope, leatherback, leopard, lizard,
   mackerel, mackerel sky, marble, marbled paper, matamata, mercury,
   moire, monitor, moon, mother-of-pearl, mugger, nacre, ocelot, opal,
   ophite, patchwork quilt, peacock, quicksilver, rainbow,
   rolling stone, sea turtle, serpentine, serpentine marble,
   shifting sands, shot silk, soft-shelled turtle, spectrum,
   stump tail, teju, temporizer, terrapin, the weather, timepleaser,
   timeserver, tortoise, tortoise shell, trimmer, tuatara, turtle,
   water, weather vane, weathercock, wheel of fortune, whirligig,
   zebra



Easton's 1897 Bible Dictionary:

Chameleon
   a species of lizard which has the faculty of changing the colour
   of its skin. It is ranked among the unclean animals in Lev.
   11:30, where the Hebrew word so translated is _coah_ (R.V.,
   "land crocodile"). In the same verse the Hebrew _tanshemeth_,
   rendered in Authorized Version "mole," is in Revised Version
   "chameleon," which is the correct rendering. This animal is very
   common in Egypt and in the Holy Land, especially in the Jordan
   valley.