Merriam-Webster Collegiate Dictionary - chameleon

 noun  Usage: often attributive  Etymology: Middle English camelion, from Middle French, from Latin chamaeleon, from Greek chamaileon, from chamai on the ground + leon lion — more at humble  Date: 14th century  1. any of a family (Chamaeleontidae) of chiefly arboreal Old World lizards with prehensile tail, independently movable eyeballs, and unusual ability to change the color of the skin  2.  a. a person given to often expedient or facile change in ideas or character  b. one that is subject to quick or frequent change especially in appearance  3. American ~  • ~ic adjective  • ~like adjective