the adder, or any of a family of snakes related to it
the adder, or any of a family of Old World snakes related to it: family Viperidae
= pit viper
a malignant or treacherous person
O villains, vipers, damn'd without redemption! — Shakespeare
viperish adj
viperous adj
[early French vipere from Latin vipera, from vivus alive + parere to bring forth; because many species of Old World vipers bear live young]