viper

American  

[vahy-per] / ˈvaɪ pər /

noun

1. any of several venomous Old World snakes of the genus Vipera, especially V. berus, a small snake common in northern Eurasia.

2. any related snakes belonging to the family Viperidae, characterized by erectile, venom-conducting fangs.

3. pit viper.

4. any of various venomous or supposedly venomous snakes.

5. a malignant or spiteful person.

6. a false or treacherous person.

7. Military. Viper, a 9-pound (4-kilogram), shoulder-launched, unguided U.S. Army antitank rocket with an effective range of 273 yards (250 meters).

---

idioms

1. to nourish a viper in one's bosom, to befriend a person who proves to be treacherous.

viper British  

/ ˈvaɪpə /

noun

1. any venomous Old World snake of the family Viperidae, esp any of the genus Vipera (the adder and related forms), having hollow fangs in the upper jaw that are used to inject venom

2. any of various other snakes, such as the horned viper

3. See pit viper

4. a malicious or treacherous person

---

Other Word Forms

• viper-like adjective
• viperish adjective
• viperishly adverb

Etymology

Origin of viper

First recorded in 1520–30; from Latin vīpera, variant of unattested vīvipera, noun use of feminine of unattested vīviper, later (as re-formation) vīviparus “bringing forth live young”; vivi-, -parous

Explanation

A viper is a certain type of poisonous snake. The most common vipers in the United States are rattlesnakes and water moccasins. Vipers are found in most places on earth and they're a diverse group with over 200 species. Vipers have specialized pits on their faces that can detect heat that's emitted from their prey, which gives them a big advantage to sense and catch their prey quickly. Viper is a scientific name for a particular family of snakes that poison others by biting them with hollow fangs that inject venom. And because of that, viper (and snake) are often used to describe spiteful, disloyal, or back-stabbing people.

Example Sentences

In 2019, officials at the Chennai airport seized a horned pit viper snake, five Iguanas, four blue-tongued skinks, three green tree frogs and 22 Egyptian tortoises from a man travelling from Thailand.

From BBC • Jun. 2, 2025

Was it a deadly viper or a harmless python?

From Science Magazine • Mar. 8, 2024

Jardine's group is now pursuing broadly neutralizing antibodies against another elapid toxin, as well as two viper toxins.

From Science Daily • Feb. 21, 2024

In 2013, biologist Alejandro Arteaga had just co-authored a book about the amphibians and reptiles of Mindo, Ecuador, complete with a beautiful, lime-colored eyelash viper on the cover.

From National Geographic • Feb. 13, 2024

‘That will stop the poisnowse juices from the venomsome viper going up your leg and into your heart!’

From "The BFG" by Roald Dahl

Related Words

• cobra