: 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
Grove’s proposal, Senate Bill 712 — dubbed Leno’s Law — would exempt vehicles 35 years or older from California’s smog check program.
—
Hector Amezcua, Sacbee.com, 9 Apr. 2025
More than any other eastern state, Connecticut has suffered from this due to prevailing wind currents dumping pollution, greenhouse gases and summertime smog here that emanate from midwestern and upwind power plants and other industrial sources.
—Jan Ellen Spiegel, Hartford Courant, 28 Mar. 2025
Cities that were once notorious for their thick, choking smog – such as Los Angeles, Houston and Pittsburgh – now see far cleaner air, while lakes and forests devastated by acid rain in the Northeast have rebounded.
—Richard E. Peltier, The Conversation, 12 Mar. 2025
The gas can form volcanic smog (vog) when exposed to the atmosphere, and long-term exposure to vog can cause irritation of the eyes, throat and lungs.
—David Faris, Newsweek, 18 Jan. 2025
See All Example Sentences for smog
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Hector Amezcua, Sacbee.com, 9 Apr. 2025
More than any other eastern state, Connecticut has suffered from this due to prevailing wind currents dumping pollution, greenhouse gases and summertime smog here that emanate from midwestern and upwind power plants and other industrial sources.
—Jan Ellen Spiegel, Hartford Courant, 28 Mar. 2025
Cities that were once notorious for their thick, choking smog – such as Los Angeles, Houston and Pittsburgh – now see far cleaner air, while lakes and forests devastated by acid rain in the Northeast have rebounded.
—Richard E. Peltier, The Conversation, 12 Mar. 2025
The gas can form volcanic smog (vog) when exposed to the atmosphere, and long-term exposure to vog can cause irritation of the eyes, throat and lungs.
—David Faris, Newsweek, 18 Jan. 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 2 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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