: 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
Every senator and all but one Republican member of the House of Representatives voted in favor of the 1970 Clean Air Act, which dramatically reduced smog and other toxic pollution throughout the country.
—
Michael Hawthorne, Chicago Tribune, 2 Apr. 2025
Pollution from vehicle tailpipes and industry (NOx and VOCs) mix with sunlight to form smog, making the summer months the worst for air quality in cities.
—Kaitlin McCallum, Hartford Courant, 1 Apr. 2025
Coal emissions can also lead to health issues, including respiratory illness, lung disease, acid rain, smog, and neurological and developmental damage.
—Kelly Livingston, ABC News, 18 Mar. 2025
California’s global leadership on environmental issues, dating back to its pioneering crusade against smog in Los Angeles in the 1940s, is an appropriate source of pride for many residents.
—U T Editorial Board, San Diego Union-Tribune, 21 Feb. 2025
See All Example Sentences for smog
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Michael Hawthorne, Chicago Tribune, 2 Apr. 2025
Pollution from vehicle tailpipes and industry (NOx and VOCs) mix with sunlight to form smog, making the summer months the worst for air quality in cities.
—Kaitlin McCallum, Hartford Courant, 1 Apr. 2025
Coal emissions can also lead to health issues, including respiratory illness, lung disease, acid rain, smog, and neurological and developmental damage.
—Kelly Livingston, ABC News, 18 Mar. 2025
California’s global leadership on environmental issues, dating back to its pioneering crusade against smog in Los Angeles in the 1940s, is an appropriate source of pride for many residents.
—U T Editorial Board, San Diego Union-Tribune, 21 Feb. 2025
See All Example Sentences for smog
Cite this Entry
“Smog.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/smog. Accessed 12 Apr. 2025.
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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