poisonous

adjective

poi·son·ous ˈpȯiz-nəs

ˈpȯi-zᵊn-əs

Synonyms of poisonous

: destructive, harmful

: having the properties or effects of poison

poisonous gas

: producing a toxic substance that causes injury or death when absorbed or ingested

poisonous mushrooms

also : venomous

a poisonous spider

: spiteful, malicious

poisonous rumors

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.

Every part of the tree is poisonous, including the small round manchineel fruits, which are known to be fatal if ingested. — Steve Bender, Southern Living, 21 June 2026 Sago palm, oleander, foxglove, azaleas and lily of the valley are all common and all poisonous. — Ryan Brennan, Miami Herald, 2 July 2026 Consuming this toxin can release poisonous hydrogen cyanide into the bloodstream. — Carrie Madormo, Verywell Health, 30 June 2026 All of this played out against an increasingly poisonous political environment. — Eric Berger, ArsTechnica, 3 July 2026 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

See more words from the same century

Browse Nearby Words

poison oak

poisonous

poison out

See all Nearby Words

Cite this Entry

Style

“Poisonous.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/poisonous. Accessed 10 Jul. 2026.

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Kids Definition

poisonous

adjective

poi·son·ous ˈpȯiz-nəs

-ᵊn-əs

: containing poison : having or causing an effect of poison

poisonously adverb

Medical Definition

poisonous

adjective

poi·son·ous ˈpȯiz-nəs, -ᵊn-əs

: having the properties or effects of poison

poisonous gas

: producing a toxic substance that causes injury or death when absorbed or ingested

poisonous frogs and plants

also : venomous

poisonous

adjective

Synonyms of poisonous

Examples of poisonous in a Sentence

Word History

Browse Nearby Words

Cite this Entry

Kids Definition

Medical Definition

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