- any of numerous venomous snakes of the family Crotalidae, of the New World, Asia, and the Malay Archipelago, as the rattlesnake, water moccasin, and copperhead, having a heat-sensitive pit on each side of the head between the eye and nostril.
- any venomous snake of the New World family Crotalidae, having a heat-sensitive organ in a pit on each side of the head: includes the rattlesnakes
