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).

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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

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Other Word Forms

Derived Forms

• viperishly
  adverb
• viper-like
  adjective
• viperish
  adjective

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”; see 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

Some populations are dark green with obvious blotches, making them fairly easy to distinguish from the redtail pit viper, which is bright green and unmarked.

From Science Daily • Apr. 21, 2026

These include the green pit viper commonly found in the northern state of Himachal Pradesh, the Malabar pit viper and hump-nosed pit viper found in southern states and many other species in the north-eastern states.

From BBC • Feb. 1, 2026

He played Tedros, a wannabe music industry impresario who also happened to be a pseudo-cult-leading viper attracted to the shiny fame of Lily-Rose Depp’s pop star, Jocelyn.

From Salon • May 19, 2025

Was it a deadly viper or a harmless python?

From Science Magazine • Mar. 8, 2024

Not surprisingly, Ella began treating me like a viper.

From "The Autobiography of Malcolm X" by Alex Malcolm X;Hailey

Related Words

• cobra