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

Perhaps even more interestingly, the bark and leaves of the Sambucus nigra are considered poisonous; the berries themselves must be cooked before consuming. —Jeanne Ballion, Vogue, 9 Feb. 2025

There is poisonous and lame political commentary all around us, and then there’s the work of Joy Reid. —Rich Lowry, National Review, 20 Jan. 2025

The smoke and ash from structures and cars can contain more than a hundred toxic chemicals and poisonous gases, according to state officials. —Tony Briscoe, Los Angeles Times, 30 Jan. 2025

Mighty Doom is a serviceable mobile game, but the change of perspective and poisonous mobile game monetization harm the franchise. —Joel Thayer, Newsweek, 26 Jan. 2025

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