: 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
The summer gasoline blend rules, which have been in effect since 1996, are intended to prevent the release of smog-causing particles into the air, the Michigan Department of Agriculture and Rural Development said.
—
Paula Wethington,
CBS News,
29 June 2026
What was once the season of patios and long days has increasingly turned into one of heat advisories, wildfire smoke, and smog alerts.
—
Alexandra Emanuelli,
Travel + Leisure,
28 June 2026
California has long held special authority under the federal Clean Air Act to set stricter emissions standards than the federal government because of the state’s historic smog problems.
—
Haley Parsley
june 22,
Sacbee.com,
23 June 2026
Bonta and environmental groups said the regulations are key to helping California continue to reduce harmful smog that worsens asthma, emphysema and heart disease.
—
Paul Rogers,
Mercury News,
22 June 2026
See All Example Sentences for smog
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Paula Wethington,
CBS News,
29 June 2026
What was once the season of patios and long days has increasingly turned into one of heat advisories, wildfire smoke, and smog alerts.
—
Alexandra Emanuelli,
Travel + Leisure,
28 June 2026
California has long held special authority under the federal Clean Air Act to set stricter emissions standards than the federal government because of the state’s historic smog problems.
—
Haley Parsley
june 22,
Sacbee.com,
23 June 2026
Bonta and environmental groups said the regulations are key to helping California continue to reduce harmful smog that worsens asthma, emphysema and heart disease.
—
Paul Rogers,
Mercury News,
22 June 2026
See All Example Sentences for smog
Cite this Entry
“Smog.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/smog. Accessed 1 Jul. 2026.
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
Love words? Need even more definitions?
Merriam-Webster unabridged
