: 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
According to Citizens’ Climate Lobby, burning fossil fuels releases a mix of harmful pollutants including carbon dioxide, sulfur dioxide, nitrogen oxides, and particulate matter that contribute to global warming, smog, acid rain, and severe respiratory illnesses.
—
Dianne Plummer, Forbes.com, 22 May 2025
However, the season, time of day, cloud coverage, smog, and sunscreen can affect how much vitamin D3 your body makes from the sun.
—Health, 20 May 2025
The turbines give off nitrogen oxides, a key contributor to smog, and formaldehyde, among other pollutants, according to their manufacturer.
—Stephanie Gosk, NBC news, 15 May 2025
In our lifetimes, cities were clogged with smog, which contained plenty of lead belched from then-leaded gasoline.
—New York Daily News Editorial Board, New York Daily News, 23 Apr. 2025
See All Example Sentences for smog
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Dianne Plummer, Forbes.com, 22 May 2025
However, the season, time of day, cloud coverage, smog, and sunscreen can affect how much vitamin D3 your body makes from the sun.
—Health, 20 May 2025
The turbines give off nitrogen oxides, a key contributor to smog, and formaldehyde, among other pollutants, according to their manufacturer.
—Stephanie Gosk, NBC news, 15 May 2025
In our lifetimes, cities were clogged with smog, which contained plenty of lead belched from then-leaded gasoline.
—New York Daily News Editorial Board, New York Daily News, 23 Apr. 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 31 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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