: 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
Fishermen battling with changing oceans chart new course after Trump’s push to deregulate
Jay Leno pushes bill to end smog checks in California for vehicles 35 years or older
A church dedicated to helping the poor and suffering can’t ignore the ravages of an overheating planet.
—
Mark Gongloff, Mercury News, 11 May 2025
As the plane began its descent into Baiyun International Airport—the busiest airport in China, handling more than 76 million passengers in 2024—the greenery gave way to concrete and skyscrapers, and the fog started to look a lot more like smog.
—Bonnie Tsui, AFAR Media, 6 May 2025
Through aerial photography and emissions information from the turbine manufacturers' specifications sheets, SELC was able to estimate the amount pollution such as nitrogen oxides, or NOx, which causes smog.
—Jeff Young, MSNBC Newsweek, 6 May 2025
That choking smog was fueled by air pollution from cars and industry, which became trapped mid-air by mountains and wind patterns.
—Camila Domonoske, NPR, 1 May 2025
See All Example Sentences for smog
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Mark Gongloff, Mercury News, 11 May 2025
As the plane began its descent into Baiyun International Airport—the busiest airport in China, handling more than 76 million passengers in 2024—the greenery gave way to concrete and skyscrapers, and the fog started to look a lot more like smog.
—Bonnie Tsui, AFAR Media, 6 May 2025
Through aerial photography and emissions information from the turbine manufacturers' specifications sheets, SELC was able to estimate the amount pollution such as nitrogen oxides, or NOx, which causes smog.
—Jeff Young, MSNBC Newsweek, 6 May 2025
That choking smog was fueled by air pollution from cars and industry, which became trapped mid-air by mountains and wind patterns.
—Camila Domonoske, NPR, 1 May 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 28 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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