noxious

/ˈnɑkʃəs/

/ˈnɒkʃəs/

Something noxious is harmful and could be even fatal — whether it is colorless, odorless, and invisible like carbon monoxide, or dark, strong-smelling, and obvious, like black smoke from a fire. People are called noxious too when they hurt others with cruelty or mental anguish.

English and Latin roots for noxious are related to the meanings of "harm," "damage," and "injury." While obnoxious might come to mind when seeing the word noxious, obnoxious is a much less damaging adjective to describe someone annoying. Most uses for noxious involve real physical or emotional damage unless the word is used in exaggeration. Examples range from "the noxious gas fumes made the dog pass out" to "his cologne was so noxious I had to exit the elevator and take the stairs."

Definitions of noxious

1. adjective

   injurious to physical or mental health
   “noxious chemical wastes”

   “noxious ideas”

   synonyms:

   harmful

   causing or capable of causing harm

   baneful, deadly, pernicious, pestilent

   exceedingly harmful

   corrupting, degrading

   harmful to the mind or morals

   vesicant, vesicatory

   causing blisters

   toxic

   of or relating to or caused by a toxin or poison

   unwholesome

   detrimental to physical or moral well-being

   antonyms:

   innocuous

   not injurious to physical or mental health

   harmless

   not causing or capable of causing harm

   innoxious

   having no adverse effect