1
a
: a common Eurasian venomous snake (Vipera berus) that attains a length of about two feet (0.6 meter), varies in color from red, brown, or gray with dark markings to black, and is usually not fatal to humans
broadly
: any of a family (Viperidae) of venomous snakes that includes Old World snakes (subfamily Viperinae) and the pit vipers
b
: a venomous or reputedly venomous snake
2
: a vicious or treacherous person
Examples of viper in a Sentence
a viper sliding silently through the field
Recent Examples on the Web
The pit vipers can be found across the eastern United States, with sightings ranging from Texas to Iowa to the Carolinas and north to Pennsylvania and New England, according to the National Zoo.
Audrey Conklin is a digital reporter for Fox News Digital and FOX Business.
—
Audrey Conklin, FOXNews.com, 11 June 2025
Finally, there’s the pit viper sub-family (Crotalinae), which includes rattlesnakes, copperheads and bushmasters.
—Scott Travers, Forbes.com, 25 Apr. 2025
Venom from snakes in the viper family rips up tissues, causing victims to bleed to death.
—Apoorva Mandavilli, New York Times, 2 May 2025
According to a study published April 23 in the journal Evolution, some vipers are producing venoms containing fewer and more focused toxins, despite living in extremely varied environments.
—Andrew Paul, Popular Science, 23 Apr. 2025
See All Example Sentences for viper
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Audrey Conklin, FOXNews.com, 11 June 2025
Finally, there’s the pit viper sub-family (Crotalinae), which includes rattlesnakes, copperheads and bushmasters.
—Scott Travers, Forbes.com, 25 Apr. 2025
Venom from snakes in the viper family rips up tissues, causing victims to bleed to death.
—Apoorva Mandavilli, New York Times, 2 May 2025
According to a study published April 23 in the journal Evolution, some vipers are producing venoms containing fewer and more focused toxins, despite living in extremely varied environments.
—Andrew Paul, Popular Science, 23 Apr. 2025
See All Example Sentences for viper
Cite this Entry
“Viper.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/viper. Accessed 19 Jun. 2025.
Copy CitationKids Definition
viper
noun
vi·per
ˈvī-pər 
1
: any of a family of poisonous snakes having heavy bodies, broad heads, and hollow tube-shaped fangs and including Old World snakes and the pit vipers
2
: any snake that is poisonous or that is believed to be poisonous
Medical Definition
viper
noun
vi·per
ˈvī-pər
1
: a common Eurasian venomous snake of the genus Vipera (V. berus) that attains a length of about two feet (0.6 meter), varies in color from red, brown, or gray with dark markings to black, and whose bite is usually not fatal to humans
broadly
: any snake of an Old World subfamily (Viperinae) of the family Viperidae
2
3
: a venomous or reputedly venomous snake
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