poisonous
Americanadjective
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full of or containing poison.
poisonous air; a poisonous substance.
-
harmful; destructive.
poisonous to animals; poisonous rumors.
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deeply malicious; malevolent.
poisonous efforts.
adjective
-
having the effects or qualities of a poison
-
capable of killing or inflicting injury; venomous
-
corruptive or malicious
Other Word Forms
- nonpoisonous adjective
- nonpoisonously adverb
- nonpoisonousness noun
- poisonously adverb
- poisonousness noun
- semipoisonous adjective
- semipoisonously adverb
- unpoisonous adjective
- unpoisonously adverb
Etymology
Origin of poisonous
Compare meaning
How does poisonous compare to similar and commonly confused words? Explore the most common comparisons:
Explanation
What do arsenic, cyanide, and bleach all have in common? They're poisonous. In other words, if you ingest these poisonous chemicals, you will most likely die or become very ill. If something is poisonous, you'd better not eat, drink, inhale, or touch it: it will make you sick. Some poisonous materials can even kill you. Of course, this adjective is derived from the noun poison, which is a toxic substance. You can also calls things poisonous if they're harmful in less physical ways. Spreading lies about someone is poisonous. Betraying a friend is poisonous. What both kinds of poisonous things have in common is that they do damage.
Vocabulary lists containing poisonous
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Harmful, List 2
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-ious, -eous, -ous
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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
In a typical year, the California Poison Control Center may receive up to five cases of poisonous mushroom-related illness, according to authorities.
From Los Angeles Times • Jan. 16, 2026
Hydrogen cyanide, which is highly poisonous, can freeze into crystals at low temperatures.
From Science Daily • Jan. 16, 2026
Once “destined for great things,” Lila makes a poisonous marriage that she eventually escapes by leaving to work in a factory.
From The Wall Street Journal • Dec. 26, 2025
We watched that big long snake slither away, but luckily it wasn’t poisonous.
From "Lost Boy, Lost Girl" by John Bul Dau
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
