monitor lizard

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various carnivorous lizards of the genus Varanus of tropical Africa, Asia, and Australasia, having a forked tongue and a long neck, and ranging in size from very small to very large.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of various large lizards of the genus Varanus, native to Africa, Asia and Australia, that are carnivorous.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any of various large tropical carnivorous lizards of Africa and Asia and Australia; fabled to warn of crocodiles