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

However, its seeds, flowers, and leaves are very poisonous. —Clarence Schmidt, San Diego Union-Tribune, 12 Mar. 2025

While shooting the scene, the snake handlers identified which snakes by color were poisonous and told Goggins not to touch them. —Lexi Carson, The Hollywood Reporter, 6 Mar. 2025

All types of wolfsbane are poisonous, and aconitum anthora is neither an antidote nor an exception. —Laura Murphy, JSTOR Daily, 28 Feb. 2025

The hotel workers keep warning guests about the monkeys—not to mention the poisonous fruit—and the episodes have been filled with ominous shots of primate statues. —Eliana Dockterman, TIME, 24 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