What are the characteristics of the animal viper?

Viper as in the snake? :- the common viper is the Viperus Berus (european adder)

Vipers are characterised by very short, fat bodies, unlike the other species of snake. They also are one of the only types of snake to have venom glands, ie pit viper, death adder, puff adder, gaboon viper, rhinocerous adder. Some species of adder have heat 'pits', in order to sent heat, hence the group 'pit vipers', contrary to popular belief very few other types of snake can do this except the viper. you know when to stay away from a snake if it is short and stocky, as it will be venomous. hope that helped a bit