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.

But the point was just that Nick’s character is emulating Sheridan’s poisonous corrupted values, and the internet is a vehicle for that relationship. — Brian Davids, HollywoodReporter, 27 Aug. 2026 Eucalyptus oil and fresh leaves are poisonous when ingested or inhaled. — Sarah Bence, Verywell Health, 25 Aug. 2026 For this reason, these poisonous mushrooms are more commonly confused with other types of edible mushrooms like chicken of the woods and chanterelles (more on these in a minute). — Katie Hill, Outdoor Life, 6 Aug. 2026 Perhaps ducks had been used as bio-processors, feeding on toads and metabolizing their poisonous compounds so that humans could safely consume them. — Kimon De Greef, Longreads, 4 Aug. 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 6 Sep. 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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