What does poisonous mean?
Poisonous describes something capable of causing poison, serious illness, or death, especially a substance, plant, animal, or fumes. The word can also be used figuratively to describe remarks, rhetoric, relationships, or influences that are malicious, corrupting, or psychologically damaging. In scientific and everyday contexts, toxic is a closely related term, but toxic is often more general, while poisonous has a strong association with substances that cause poisoning. The figurative use is especially common in discussion of language, media, and interpersonal behavior. The word’s history comes through its connection with poison, from Old French poison, ultimately traced to Latin vocabulary associated with drinking and harmful substances. Knowing the distinction between poisonous and venomous can also help: venomous organisms actively deliver poison, while poisonous organisms or substances are dangerous when contacted, consumed, or inhaled.
adjectiveCapable of causing poisoning or death when eaten, touched, inhaled, or otherwise encountered. It can also describe ideas, remarks, or influences that are deeply harmful, corrupting, or destructive.
- Able to cause poisoning, illness, or death.
- Causing serious harm, corruption, or emotional damage; especially used figuratively of remarks, relationships, influences, and rhetoric.
"The fungus is beautiful, but it is poisonous and should never be touched."
"Several poisonous mushrooms were found near the trail."
"Her poisonous accusation turned the conversation into a public argument."
A poisonous word can wound an audience just as surely as a poisonous plant can wound the hand that touches it.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does poisonous come from?
The adjective derives from the same historical vocabulary as the noun poison. The English noun comes through Old French poison from Latin potio, a stem also represented in words such as potion and potable, relating broadly to drinking and what is consumed. Over time, the adjective came to describe substances capable of causing poisoning and, figuratively, things that are profoundly harmful.
Related word forms
How poisonous is actually used
The word is common in both formal and informal English. In figurative use, it often conveys a stronger sense of persistent or malicious harm than the more neutral word harmful.
Easily confused with poisonous
Venomous usually describes an animal, insect, or plant that delivers poison through a bite, sting, or similar mechanism, whereas poisonous more broadly describes a substance or organism that is harmful when touched, eaten, or inhaled.
Toxic is broader and can mean poisonous or dangerously harmful, including in figurative contexts such as toxic relationships, while poisonous is especially common for substances that can cause poisoning.