poisonous
Americanadjective
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full of or containing poison.
poisonous air; a poisonous substance.
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harmful; destructive.
poisonous to animals; poisonous rumors.
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deeply malicious; malevolent.
poisonous efforts.
adjective
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having the effects or qualities of a poison
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capable of killing or inflicting injury; venomous
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corruptive or malicious
Other Word Forms
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.
The azure shimmer of the blue morpho confuses predators, while monarchs’ vibrant orange-and-black wings warn birds and other predators that they are poisonous.
From The Wall Street Journal ● Aug. 3, 2026
The Pluskal Group, including Mutabdžija, was studying the same difficult family of diterpenoid alkaloids in wolfsbane, a famously poisonous relative of larkspur that is also known as monkshood.
From Science Daily ● Aug. 3, 2026
For his part, during his by-election campaign, Burnham warned voters that Britain risked drifting towards the "polarised, poisonous politics" of the United States, where "people in communities don't work together any more".
From Barron's ● Jul. 19, 2026
Although this may sound alarming, a number of poisonous plants can be found in ordinary gardens in the UK, with people completely unaware of their dangerous potential.
From BBC ● Jul. 1, 2026
Tess’s mother left the window and leaned back into the corner, as if three kids were poisonous and she was afraid to come too close.
From "As Brave As You" by Jason Reynolds
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.
