1. harmful or injurious to health or physical well-being: noxious fumes.
  2. morally harmful; corrupting; pernicious: a noxious plan to spread dissension.

Origin of noxious

1605–15; < Latin noxius harmful, hurtful, injurious, equivalent to nox(a) harm, hurt, injury (akin to nocēre to do harm, inflict injury; see innocent) + -ius -ious
Related formsnox·ious·ly, adverbnox·ious·ness, noun

Synonyms for noxious

Antonyms for noxious

1, 2. harmless. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for noxiously


  1. poisonous or harmful
  2. harmful to the mind or morals; corrupting
Derived Formsnoxiously, adverbnoxiousness, noun

Word Origin for noxious

C17: from Latin noxius harmful, from noxa injury
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for noxiously



c.1500, from Latin noxius "hurtful, injurious," from noxa "injury, hurt, damage entailing liability" (related to nocere "to hurt," and to nex "slaughter"), from PIE *nek-ro-, causative form of root *nek- "death" (see necro-).

Online Etymology Dictionary, © 2010 Douglas Harper

noxiously in Medicine


  1. Harmful to living things; injurious to health.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.