: 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
Southern California has been choked by smog since the mass adoption of the automobile.
—
Terry Castleman, Los Angeles Times, 23 Apr. 2025
In 2023, nearly half of the country's inhabitants — 156 million people — lived in places heavy in smog or soot pollution that harms their lungs, hearts, and brains, according to the newest edition of the American Lung Association's State of the Air report.
—Alejandra Borunda, NPR, 23 Apr. 2025
Wildfires burning in Canada in the summer of 2023 blanketed the Upper Midwest and Northeast with smog and high levels of particulate pollution.
—Michael Loria, USA Today, 23 Apr. 2025
One case stems from a dispute over whether Oklahoma and Utah must create better plans to fight smog, while the other concerns whether some oil refineries can skirt requirements that their gasoline contains a percentage of ethanol.
—Ella Lee, The Hill, 29 Jan. 2025
See All Example Sentences for smog
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Terry Castleman, Los Angeles Times, 23 Apr. 2025
In 2023, nearly half of the country's inhabitants — 156 million people — lived in places heavy in smog or soot pollution that harms their lungs, hearts, and brains, according to the newest edition of the American Lung Association's State of the Air report.
—Alejandra Borunda, NPR, 23 Apr. 2025
Wildfires burning in Canada in the summer of 2023 blanketed the Upper Midwest and Northeast with smog and high levels of particulate pollution.
—Michael Loria, USA Today, 23 Apr. 2025
One case stems from a dispute over whether Oklahoma and Utah must create better plans to fight smog, while the other concerns whether some oil refineries can skirt requirements that their gasoline contains a percentage of ethanol.
—Ella Lee, The Hill, 29 Jan. 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 13 May. 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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