puff adder

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A venomous African viper (Bitis arietans) having crescent-shaped yellowish markings.
2. n. See hognose snake.

Century Dictionary and Cyclopedia

1. n. The largest and most venomous African serpent of the family Viperidæ, Clotho arietans. It lies with its body partly immersed in the sand, its head only being exposed, so that pedestrians are liable to tread on it. It is sluggish in its nature, and the Bushman will fearlessly put his foot on its neck, and then cut off its head for the sake of its venom, with which he poisons his arrows. It is, when full-grown, from 4 to 5 feet long, and as thick as a man's arm. It is named from its habit of puffing up the upper part of its body when irritated. See cut under Viperidæ. Compare puffing-adder.

Wiktionary

1. n. Alternative form of puffadder.

GNU Webster's 1913

1. n. (Zoöl.) A North American harmless snake (Heterodon platyrrhinos) which has the power of puffing up its body. Called also hog-nose snake, flathead, spreading adder, and blowing adder.

WordNet 3.0

1. n. harmless North American snake with upturned nose; may spread its head and neck or play dead when disturbed
2. n. large African viper that inflates its body when alarmed