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

But left unchecked, fear of failure becomes poisonous. —Mark Kane, Forbes, 9 Dec. 2024

But the film’s poisonous reviews and disastrous box office all but torpedoed her Oscar hopes this year, and the film was shut out in Monday’s Globe nominations. —Patrick Ryan, USA TODAY, 9 Dec. 2024

The leaves do have a milky sap that can cause a rash in some people if they are exposed to it, but the plants are not poisonous. —Janet B. Carson, arkansasonline.com, 2 Dec. 2024

Australia is famous for its deadly creatures, including a wide variety of sharks, snakes and two of the world’s most poisonous spiders. —Hanna Ziady, CNN, 1 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