Definitions

poisonous

[poi-zuh-nuhs] / ˈpɔɪ zə nəs /

ADJECTIVE

harmful

Synonyms

STRONGEST

dangerous deadly destructive fatal lethal noxious pernicious toxic venomous vicious virulent

WEAK

bad baleful baneful corrupt corruptive deleterious detrimental evil hurtful infective malicious malignant mephitic miasmatic morbid mortal nocuous noisome peccant pestiferous pestilential poison septic toxicant toxiferous viperous

Antonyms

STRONGEST

gentle good harmless healthful healthy helpful kind life-giving nice nonpoisonous wholesome

WEAK

benevolent non-toxic

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

It’s got poisonous lead in it from paint.

From Salon • Mar. 6, 2026

But time and again the poisonous isolation that absolute power imposes on its wielders blunted the edge of their insight and degraded the capacity of their societies.

From The Wall Street Journal • Jan. 26, 2026

Whether you have sympathy for him, think his behaviour is appalling, or something in between, there's clearly a poisonous row raging over what he did.

From BBC • Jan. 17, 2026

The death cap is the world’s most poisonous mushroom, responsible for 90% of mushroom-related fatalities.

From Los Angeles Times • Jan. 16, 2026

The spiders were communicating once more, slowly rubbing their great ribbed back legs together like poisonous crickets.

From "Rowan of Rin" by Emily Rodda

Vocabulary lists containing poisonous

Week 4 Vocabulary

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Harmful, List 2

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-ious, -eous, -ous

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