Any of certain American venomous snakes having a series of horny interlocking joints at the end of the tail which make a sharp rattling sound when shaken. A smaller form known as the Massassaugas or pygmy rattlesnakes were found in swampy ares. A larger form the yellow or timber rattlesnake live along rocky ledges. Though they are rather thick-bodied, large headed snakes, they are of a sluggish disposition and are not inclined to bite except when disturbed or in pursuit of prey. Earl.y settlers around the canal often killed rattlesnakes.