smog

American  

[smog, smawg] / smɒg, smɔg /

noun

1. smoke or other atmospheric pollutants combined with fog in an unhealthy or irritating mixture.

2. photochemical smog.

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verb (used with object)

1. to cover or envelop with or as if with smog.

smog British  

/ smɒɡ /

noun

1. a mixture of smoke, fog, and chemical fumes

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smog Scientific  

/ smŏg /

1. A form of air pollution produced by the reaction of sunlight with hydrocarbons, nitrogen compounds, and other gases primarily released in automobile exhaust. Smog is common in large urban areas, especially during hot, sunny weather, where it appears as a brownish haze that can irritate the eyes and lungs. Ozone, a toxic gas that is not normally produced at lower atmospheric levels, is one of the primary pollutants created in this kind of smog.

2. Also called photochemical smog

3. Fog that has become polluted with smoke and particulates, especially from burning coal.

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smog Cultural  

1. A haze or fog composed of water vapor, complex molecules, and suspended particles.

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Discover More

In North America, the primary cause of smog is pollution from automobile exhaust.

The Los Angeles basin, where pollutants can be trapped by inversions and the surrounding mountains, has frequent problems with smog, as do other major urban areas.

The word smog is a combination of smoke and fog.

Other Word Forms

Derived Forms

• desmog
  verb (used with object)
• smoggy
  adjective
• smogless
  adjective

Etymology

Origin of smog

1900–05; sm(oke) + ( f)og ¹

Explanation

What do you get when you combine "smoke" and "fog"? Smog! Smog is the thick haze or smoke that's caused by polluting substances in the air. Generally, the more cars there are in a city, the more likely there is to be smog. There are other culprits for smog, though, including coal-burning factories, other chemical emissions from plants and mills, and nearby forest fires. If there's too much smog in a city, it can make it hard for people with asthma to breathe.Smog is a great example of a portmanteau, a word formed by combining two other words into one: it comes from smoke and fog.

Example Sentences

And, for all the talk of smog worries, data from Growth Energy shows E15 reduces smog-forming pollutants.

From The Wall Street Journal • Jun. 3, 2026

One problem is that ethanol blends greater than 10% can increase smog during warm weather, which is why the EPA restricts its sale during the summer.

From The Wall Street Journal • May 10, 2026

Summer gas is refined in a way that reduces emissions and smog, but it is also costlier to make.

From MarketWatch • Apr. 29, 2026

E15 is less expensive than regular diesel, but is restricted due to the smog it creates.

From Salon • Apr. 25, 2026

But Tehran’s air was regular city air, with a tang of smog to it, and a bit less of Portland’s rain-soaked earth smell.

From "Darius the Great Is Not Okay" by Adib Khorram

Related Words

• acid rain
• carbon dioxide
• fog
• smoke
• soot