noxious

adjective

nox·​ious ˈnäk-shəs How to pronounce noxious (audio)
Synonyms of noxiousnext
1
a
: physically harmful or destructive to living beings
noxious waste
noxious fumes
b
: constituting a harmful influence on mind or behavior
especially : morally corrupting
noxious doctrines
2
: disagreeable, obnoxious
this noxious political scandal—H. L. Ickes
noxiously adverb
noxiousness noun

Synonyms

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Choose the Right Synonym for noxious

pernicious, baneful, noxious, deleterious, detrimental mean exceedingly harmful.

pernicious implies irreparable harm done through evil or insidious corrupting or undermining.

the claim that pornography has a pernicious effect on society

baneful implies injury through poisoning or destroying.

the baneful notion that discipline destroys creativity

noxious applies to what is both offensive and injurious to the health of a body or mind.

noxious chemical fumes

deleterious applies to what has an often unsuspected harmful effect.

a diet found to have deleterious effects

detrimental implies obvious harmfulness to something specified.

the detrimental effects of excessive drinking

Examples of noxious in a Sentence

mixing bleach and ammonia can cause noxious fumes that can seriously harm you noxious smog that for years has been encrusting the historic cathedral with soot
Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
State law specifically names these three plants as noxious weeds: Municipalities can add to this list based on recommendations from the Wisconsin Department of Natural Resources' invasive species list. —Quinn Clark, jsonline.com, 25 July 2025 While seven out of 10 Indians are exposed to noxious air, pregnant women and their unborn children are among the most impacted. —Anuradha Varanasi, Forbes.com, 23 July 2025 Though Indian boarding schools still forcibly sheared children’s hair, Jones’s orders for adult men proved too noxious to enforce. —Margaret Talbot, New Yorker, 21 July 2025 Imagine putting in all that effort to scrub your bathroom from top to bottom, only to be left with noxious floral notes that are not at all appealing. —Patricia Shannon, Southern Living, 17 July 2025 See All Example Sentences for noxious

Word History

Etymology

Middle English noxius, borrowed from Latin noxius "guilty, delinquent, harmful, injurious" (derivative of noxa "injurious behavior, harm, mischief") + -us -ous; noxa derivative (perhaps with -s- as a desiderative suffix) from the base of nocēre "to damage (things), injure, harm (persons)," going back to Indo-European *noḱ-éi̯e- "destroy" (with semantic weakening in Latin), whence also Sanskrit nāśáyati "(s/he) destroys," causative derivatives from a verbal base *neḱ- "disappear, pass out of existence, perish," whence, with varying ablaut grades, Sanskrit náśyati "(s/he) is lost, perishes," Avestan nąsat̰ "has gone away, is lost," Tocharian B näk- "destroy," (in middle voice) "disappear, be destroyed"

Note: The Indo-European verbal base *neḱ- is also the source of a root noun attested as Latin nec-, nex "violent death, killing"; see necro-.

First Known Use

15th century, in the meaning defined at sense 1a

Time Traveler
The first known use of noxious was in the 15th century

Rhymes for noxious

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Browse Nearby Words

noxal surrender
noxious
noyade
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Cite this Entry

“Noxious.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/noxious. Accessed 29 Jul. 2025.

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Kids Definition

noxious

adjective
nox·​ious ˈnäk-shəs How to pronounce noxious (audio)
: harmful especially to health : unwholesome
noxious fumes

Medical Definition

noxious

adjective
nox·​ious ˈnäk-shəs How to pronounce noxious (audio)
: physically harmful or destructive to living beings
noxious wastes

More from Merriam-Webster on noxious

Nglish: Translation of noxious for Spanish Speakers

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