: 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
Fed up with the government’s inaction, a group of residents created Polish Smog Alert, an advocacy organization pushing for legislation to suppress the smog.
—
Cecilia Rodriguez, Forbes.com, 29 June 2025
The poor air quality is forecast to be an orange ozone alert, which means an unhealthy level of ground-level ozone, known as ozone pollution or smog, is expected for people sensitive to pollution, according to the agency, known as MARC.
—Ramal Nasim, Kansas City Star, 18 June 2025
The base experiences temperatures exceeding 100 degrees Fahrenheit and persistent poor air quality because of local burn pits, which emit smog and have caused respiratory illness among both officers and detainees.
—Billal Rahman, MSNBC Newsweek, 6 June 2025
How about no smog checks for cars with a consistently low smog reading?
—Jim Radcliffe, Oc Register, 23 May 2025
See All Example Sentences for smog
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Cecilia Rodriguez, Forbes.com, 29 June 2025
The poor air quality is forecast to be an orange ozone alert, which means an unhealthy level of ground-level ozone, known as ozone pollution or smog, is expected for people sensitive to pollution, according to the agency, known as MARC.
—Ramal Nasim, Kansas City Star, 18 June 2025
The base experiences temperatures exceeding 100 degrees Fahrenheit and persistent poor air quality because of local burn pits, which emit smog and have caused respiratory illness among both officers and detainees.
—Billal Rahman, MSNBC Newsweek, 6 June 2025
How about no smog checks for cars with a consistently low smog reading?
—Jim Radcliffe, Oc Register, 23 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 10 Jul. 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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