poisonous

adjective

poi·​son·​ous ˈpȯiz-nəs 

ˈpȯi-zᵊn-əs

1

: destructive, harmful

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

: spiteful, malicious

poisonously adverb

Synonyms

• envenomed
• poison
• poisoned
• toxic
• venomous

Examples of poisonous in a Sentence

Chocolate is poisonous to dogs.

This species of spider is extremely poisonous.

Recent Examples on the Web

Seven-percent mortgages have been poisonous to homebuilders, and Horton was down 26% in the fourth quarter – in a rising market, at that. —John Dorfman, Forbes, 20 Jan. 2025

Social platforms are poised to become even more poisonous to their own users as a handful of outrageously rich and powerful men grapple with their own insecurities around masculinity and free speech. —Megan Farokhmanesh, WIRED, 15 Jan. 2025

Mushrooms sold from a truck in a Salinas parking lot turned out to be poisonous, sending three people to the hospital, California health officials warned. —Don Sweeney, Sacramento Bee, 6 Jan. 2025

And there were giant spiders that were poisonous and stuff on the edge of the trees. —Nick Romano, EW.com, 18 Dec. 2024

Word History

First Known Use

15th century, in the meaning defined at sense 2

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 

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