diamondback rattlesnake

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

• noun Either of two large venomous rattlesnakes (Crotalus adamanteus or C. atrox) found in the southern and western United States and in Mexico and having diamond-shaped markings on the back.

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

• noun Either of two venomous rattlesnakes, of the genus Crotalus, from southern United States and Mexico, that have diamond-shaped markings on their backs: Crotalus adamanteus and Crotalus atrox.

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

• noun large deadly rattlesnake with diamond-shaped markings