What does noxious mean?
Noxious is an adjective meaning harmful, poisonous, or dangerous, especially to health or well-being. It is often used for fumes, chemicals, gases, substances, and other environmental hazards: “The laboratory released noxious fumes.” The word can also describe an influence or situation as seriously damaging, though this figurative use is less common. Noxious is more formal and emphatic than “bad” and more specific than “harmful,” suggesting a substantial risk rather than every minor inconvenience. Its strong negative connotation makes it useful when describing pollution, toxins, dangerous exposure, or circumstances that threaten physical health. The word comes from Latin and has long conveyed the idea of injury, poison, or destructive harm. It remains recognizable in modern environmental, medical, and public-health language, where precision about the severity of a hazard matters.
adjectiveHarmful, poisonous, or potentially dangerous to health or well-being. It can also describe something that causes serious harm, damage, or unpleasant effects.
- Harmful, poisonous, or dangerous to health or well-being.
- Capable of causing serious harm, damage, or adverse effects.
"The factory was accused of releasing noxious fumes into the surrounding neighborhood."
"Workers wore protective masks because the paint produced noxious fumes."
"The policy was condemned as a noxious influence on public life."
From the Latin noxa, meaning harm or injury, noxious describes whatever is not merely unpleasant but genuinely dangerous.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does noxious come from?
The adjective comes from Latin noxius, meaning “harmful” or “injurious,” from noxa, “harm, injury,” which is related to nocere, “to hurt.” The same broad etymological family includes Latin-derived noxia and the archaic adjective nocuous, meaning harmful. Innocuous also belongs to this semantic and etymological family through Latin roots associated with harm, but the prefix in- reverses the meaning to “harmless.”
Related word forms
How noxious is actually used
The word is formal and relatively uncommon in everyday speech. It is stronger and more specific than simply “bad,” especially when describing substances, fumes, conditions, or influences that pose a genuine risk of harm.
Easily confused with noxious
Noxious is the common modern adjective for something harmful or poisonous, while nocuous is a much rarer word with essentially the same meaning.
Noxious means actively harmful or dangerous, whereas innocuous means harmless and unlikely to cause offense.