RATTLESNAKE - (n.) Any one of several species of venomous American snakes belonging to the genera Crotalus and Caudisona, or Sistrurus. They have a series of horny interlocking joints at the end of the tail which make a sharp rattling sound when shaken. The common rattlesnake of the Northern United States (Crotalus horridus), and the diamond rattlesnake of the South (C. adamanteus), are the best known. See Illust. of Fang.