: 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
On Tuesday, the day after a night of Diwali celebrations, New Delhi woke up to a shroud of smog.
—
Robert Birsel, MSNBC Newsweek, 21 Oct. 2025
Environmental disasters like the Cuyahoga River fires and smog crises produced the Clean Air and Clean Water Acts.
—Nick Lichtenberg, Fortune, 9 Oct. 2025
From maintenance, like oil changes, fluid checks and tire, brake, and battery inspections, to a variety of repairs, and even smog tests, service is available for all makes, fleet vehicles, hot rods, classic cars and hybrids.
—Shawn Price, Oc Register, 19 Sep. 2025
Mold spores and rust bloom around the bathroom fixtures, and a mysterious black smog pours from her vents and sticks to her walls.
—Ilana Arougheti, Kansas City Star, 18 Sep. 2025
See All Example Sentences for smog
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Robert Birsel, MSNBC Newsweek, 21 Oct. 2025
Environmental disasters like the Cuyahoga River fires and smog crises produced the Clean Air and Clean Water Acts.
—Nick Lichtenberg, Fortune, 9 Oct. 2025
From maintenance, like oil changes, fluid checks and tire, brake, and battery inspections, to a variety of repairs, and even smog tests, service is available for all makes, fleet vehicles, hot rods, classic cars and hybrids.
—Shawn Price, Oc Register, 19 Sep. 2025
Mold spores and rust bloom around the bathroom fixtures, and a mysterious black smog pours from her vents and sticks to her walls.
—Ilana Arougheti, Kansas City Star, 18 Sep. 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 30 Oct. 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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