rattlesnake [ME, ratelen + AS, snacan, to creep] , a poisonous pit viper with a series of loosely connected, horny segments at the end of the tail that make a noise like a rattle when shaken. More than 25 species of rattlesnakes are found in the Americas, including most parts of the United States and Canada. They have a hematoxin in their venom, and they are responsible for most of the poisonous snake bites in the United States. Immediate treatment includes keeping the victim quiet and immobilizing the bite area at the level of the heart. Antivenin is available. Also called rattler. See also snakebite.
