: 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 purifier works with different filters, depending on your needs: a toxin absorber filter specializes in smog, toxins, and VOCs, the smoke remover filter specializes in wildfire and smoke pollution, and the pet allergy filter clears away our furry friends’ dander and unpleasant smells.
—
Ho Lin, Miami Herald, 3 Mar. 2025
These VOCs contribute to ground-level ozone and smog, which can cause respiratory issues and environmental damage.
—Robert Rapier, Forbes, 23 Feb. 2025
While lava flows remain confined to the Kīlauea summit caldera, the eruption produces hazards such as volcanic gas emissions, vog (volcanic smog) and Pele's hair—a type of volcanic glass—that can pose health risks and environmental challenges.
—Jonathan Granoff, Newsweek, 28 Jan. 2025
This radiation can hit nitrogen oxides (NOx) and volatile organic compounds (VOCs), setting off a complex set of reactions that usually results in another secondary pollutant: ozone, the main component of smog, which can damage the lungs.
—Allison Parshall, Scientific American, 13 Jan. 2025
See All Example Sentences for smog
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Ho Lin, Miami Herald, 3 Mar. 2025
These VOCs contribute to ground-level ozone and smog, which can cause respiratory issues and environmental damage.
—Robert Rapier, Forbes, 23 Feb. 2025
While lava flows remain confined to the Kīlauea summit caldera, the eruption produces hazards such as volcanic gas emissions, vog (volcanic smog) and Pele's hair—a type of volcanic glass—that can pose health risks and environmental challenges.
—Jonathan Granoff, Newsweek, 28 Jan. 2025
This radiation can hit nitrogen oxides (NOx) and volatile organic compounds (VOCs), setting off a complex set of reactions that usually results in another secondary pollutant: ozone, the main component of smog, which can damage the lungs.
—Allison Parshall, Scientific American, 13 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 24 Mar. 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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