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

In 1925: Allied powers in the League of Nations signed the Geneva Protocol, which reaffirmed prior bans on using poisonous gas in warfare and added the prohibition of bacteriological weapons. —Lorenzino Estrada, The Arizona Republic, 17 June 2024

Monarchs lay their eggs on milkweed plants, where caterpillars devour leaves containing poisonous cardiac glycosides compounds. —Brian Handwerk, Smithsonian Magazine, 12 June 2024

All this poisonous corporate thinking leads to a strong trickle-down effect, especially at a major corporate music festival like Gov Ball, which had a serious genre segregation problem this year. —Devon Ivie, Vulture, 10 June 2024

The heat from this ignition starts the decomposition of the sodium azide, which is poisonous, and the generation of nitrogen gas to fill the air bag in seconds. —Phoebe Wall Howard, Detroit Free Press, 27 Feb. 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