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

Until this cycle of indoctrination of this poisonous hatred is stopped, there’s no chance in hell for real peace for the Middle East. —David Draiman, The Hollywood Reporter, 8 Mar. 2025

Both Hackman and Arakawa tested negative for carbon monoxide poisoning, Mendoza said, but added that the pathologist would be the one to rule out the poisonous gas as the cause of death. —Marlene Lenthang, NBC News, 28 Feb. 2025

Now, finally, there’s an antidote to this poisonous narrative: Apple Cider Vinegar, a new Netflix miniseries that inverts the traditional tropes with empathy and honesty. —Alan Levinovitz, Washington Examiner - Political News and Conservative Analysis About Congress, the President, and the Federal Government, 28 Feb. 2025

This trip is hardly a vacation, though Sofia makes the most of their cottage near the sea to swim (among poisonous jellyfish) and explore (with the similarly ephemeral and no less dangerous Ingrid, seductively played by Vicky Krieps). —Peter Debruge, Variety, 14 Feb. 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