smog

noun

ˈsmäg 

ˈsmȯg

: 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

smogless

ˈsmä-gləs 

ˈsmȯ-

adjective

Synonyms of smog

• haze
• fog
• cloud
• mist

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

Within just hours of being emitted, this mixture reacts to form ground-level ozone, which can irritate the lungs and is a key component of smog. — Michael A. Robinson, The Conversation, 25 Aug. 2026

Michigan still collects state gas taxes, but revoked the annual requirement for a summer blend of gasoline in Southeast Michigan, a step that is intended to help prevent smog. — Paula Wethington, CBS News, 24 Aug. 2026

According to a legislative analysis, a 1982 vehicle that passed a smog check produced 123 times as much smog-forming pollution as a 2025 vehicle. — John Woolfolk, Mercury News, 14 Aug. 2026

Under current law, cars over 35 years old may also be exempt from specific portions of the smog test as long as they are legally classified and insured as collector motor vehicles. — Sofia Williams, Sacbee.com, 13 Aug. 2026

Word History

Etymology

smoke + fog

First Known Use

1880, in the meaning defined above

Phrases Containing smog

• anti-smog

Rhymes for smog

• blog
• bog
• clog
• cog
• dog
• flog
• fog
• frog
• grog
• hog
• jog
• log

Kids 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

Medical Definition

smog

noun

ˈsmäg also ˈsmȯg

: 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