: a fog made heavier and darker by smoke and chemical fumes
also
: a photochemical haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen especially from automobile exhaust
Examples of smog in a Sentence
the city's smog was once so bad that darkness often prevailed, even at noon
Recent Examples on the Web
Those toxins combine on hot summer days to form smog.
—
Noelle Phillips, The Denver Post, 1 Feb. 2024
Why? Go inside the long-running, sophisticated and surprisingly widespread scheme to cheat on smog tests the feds just cracked down on.
—Ryan Fonseca, Los Angeles Times, 5 Apr. 2024
See all Example Sentences for smog 
Noelle Phillips, The Denver Post, 1 Feb. 2024
Why? Go inside the long-running, sophisticated and surprisingly widespread scheme to cheat on smog tests the feds just cracked down on.
—Ryan Fonseca, Los Angeles Times, 5 Apr. 2024
See all Example Sentences for smog
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'smog.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
Dictionary Entries Near smog
Cite this Entry
“Smog.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/smog. Accessed 3 May. 2024.
Copy CitationKids Definition
smog
noun
ˈsmäg 
also ˈsmȯg
: a thick haze caused by the action of sunlight on air polluted especially by smoke and automobile exhaust fumes
Etymology
from smoke and fog
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