A coiled Pacific rattlesnake.
rattlesnake definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
any of various poisonous American pit vipers (genera Crotalus and Sistrurus), having an interlocking series of horny rings at the end of the tail that produce a rattling or buzzing sound when shaken
rattlesnake definition by American Heritage Dictionary
Any of various venomous New World snakes of the genera Crotalus and Sistrurus, having at the end of the tail a series of loosely attached, horny segments that can be vibrated to produce a rattling or buzzing sound.