poisonous

adjective

poi·​son·​ous ˈpȯiz-nəs How to pronounce poisonous (audio)
ˈpȯi-zᵊn-əs
1
2
a
: having the properties or effects of poison
poisonous gas
b
: producing a toxic substance that causes injury or death when absorbed or ingested
poisonous mushrooms
also : venomous
a poisonous spider
3
poisonously adverb

Examples of poisonous in a Sentence

Chocolate is poisonous to dogs. This species of spider is extremely poisonous.
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Almost every state has a variety of snake species, both poisonous and nonvenomous. Janet Loehrke, USA Today, 11 July 2025 This Kidde portable carbon monoxide detector uses batteries and is compact enough to slip into your carry-on, giving you peace of mind that your hotel room or Airbnb is free of poisonous levels of carbon monoxide. Amelia McBride, Travel + Leisure, 10 July 2025 In this story, money is framed as a poisonous substance, a mind virus. Dani Di Placido, Forbes.com, 10 July 2025 Knowing that he's developed a bond with Dr. Ochoa, Tessa stages a scene in which John Perry (Ian McQuown), a member of the network, attempts to kill Dr. Ochoa via one of Voit's favorite methods: a poisonous Sicarius spider dropped into her mouth. Randall Colburn, EW.com, 10 July 2025 See All Example Sentences for poisonous

Word History

First Known Use

15th century, in the meaning defined at sense 2

Time Traveler
The first known use of poisonous was in the 15th century

Browse Nearby Words

Cite this Entry

“Poisonous.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/poisonous. Accessed 23 Jul. 2025.

Kids Definition

poisonous

adjective
poi·​son·​ous ˈpȯiz-nəs How to pronounce poisonous (audio)
-ᵊn-əs
: containing poison : having or causing an effect of poison
poisonously adverb

Medical Definition

poisonous

adjective
poi·​son·​ous ˈpȯiz-nəs, -ᵊn-əs How to pronounce poisonous (audio)
1
: having the properties or effects of poison
poisonous gas
2
: producing a toxic substance that causes injury or death when absorbed or ingested
poisonous frogs and plants
also : venomous

More from Merriam-Webster on poisonous

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!