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

The bill also had money to make solvent the World Trade Center Health Program to treat the heroes and victims of 9/11 who were sickened by the poisonous air rising up from Ground Zero. —New York Daily News Editorial Board, New York Daily News, 20 Dec. 2024

In the wake of a global catastrophe where a poisonous cloud is killing everything alive, a group of family and friends gather for one last night of revelry. —Huntley Woods, EW.com, 19 Dec. 2024

Burning dirty gas inside our homes and buildings releases nitrogen oxides (NOx), a family of poisonous, highly reactive gases. —Susan Miller, Baltimore Sun, 19 Dec. 2024

Another recall was called on Friday, December 13, over supplements found to contain yellow oleander, a poisonous plant that is the subject of an FDA safety alert involving more than 20 products. —Thomas G. Moukawsher, Newsweek, 17 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