: 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
New electrification rules for a four-county area, when fully implemented, will slash nitrogen oxide pollution by 5.6 tons per day – comparable to cutting half of all smog emissions from the region’s cars.
—
Cameron Pugh, The Christian Science Monitor, 5 Aug. 2024
However, the new emission reduction rule can become effective only if the U.S. Environmental Protection Agency signs off on the region’s smog plan and approves the state regulations for locomotives and truck fleets.
—Tony Briscoe, Los Angeles Times, 2 Aug. 2024
The smog in Beijing on the eve of the Games was godawful, and wearing a thin piece of cloth—or maybe a gas mask—seemed like a smart idea.
—Frederick Dreier, Outside Online, 26 July 2024
Without so many cars, there was little smog, and the ocean breezes kept the temperature down.
—Les Carpenter, Washington Post, 21 July 2024
See all Example Sentences for smog 
Cameron Pugh, The Christian Science Monitor, 5 Aug. 2024
However, the new emission reduction rule can become effective only if the U.S. Environmental Protection Agency signs off on the region’s smog plan and approves the state regulations for locomotives and truck fleets.
—Tony Briscoe, Los Angeles Times, 2 Aug. 2024
The smog in Beijing on the eve of the Games was godawful, and wearing a thin piece of cloth—or maybe a gas mask—seemed like a smart idea.
—Frederick Dreier, Outside Online, 26 July 2024
Without so many cars, there was little smog, and the ocean breezes kept the temperature down.
—Les Carpenter, Washington Post, 21 July 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 8 Oct. 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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