fog

1 of 2

noun

ˈfȯg 

fäg

1

a

: vapor condensed to fine particles of water suspended in the lower atmosphere that differs from cloud only in being near the ground

b

: a fine spray or a foam for firefighting

2

: a murky condition of the atmosphere or a substance causing it

3

a

: a state of confusion or bewilderment

spent the morning in a fog

b

: something that confuses or obscures

hid behind a fog of rhetoric

4

: cloudiness or partial opacity in a developed photographic image caused by chemical action or stray radiation

fogless

ˈfȯg-ləs 

ˈfäg-

adjective

fog

2 of 2

verb

fogged; fogging

transitive verb

1

: to cover, envelop, or suffuse with or as if with fog

fog the barns with pesticide

2

: to make obscure or confusing

accusations which fogged the real issues

3

: to make confused

4

: to produce fog on (something, such as a photographic film) during development

intransitive verb

1

: to become covered or thick with fog

2

a

: to become blurred by a covering of fog or mist

—often used with up

My glasses keep fogging up.

b

: to become indistinct through exposure to light or radiation

Synonyms of fog

Noun

• daze
• haze

Verb

• confuse
• cloud
• blur
• muddy
• obfuscate

Examples of fog in a Sentence

Noun

Heavy fog made it difficult to see the road.

a climate marked by heavy fogs

The fog reduced visibility to a quarter of a mile.

This problem has me in a fog.

Verb

The steam from the pot was fogging the window near the stove.

The bathroom was all fogged up after my shower.

politicians who try to fog the issue instead of taking a stand

Recent Examples on the Web

Noun

Others have sought to use cloud seeding to disperse fog at airports, tackle air pollution, reduce hail damage or even to manipulate the weather for major events, such as the 2008 Summer Olympics in Beijing. —Sam Meredith, CNBC, 24 Feb. 2026

If, in the following days, increasing moisture and a sticky feel to the atmosphere are accompanied by fog or overcast skies, this can signal the approach of a cold front with a cooler air mass behind it. —Newsroom Meteorologist, Austin American Statesman, 24 Feb. 2026

Verb

De-Fog Mirrors Before getting in the shower and using shampoo on your hair, use shampoo to prevent your bathroom mirror from fogging up from the shower’s humidity. —Hallie Milstein, Southern Living, 16 Feb. 2026

Texans are waking up to fog in some areas due to calm winds and Saturday's rain. —Michael Autovino, CBS News, 16 Feb. 2026

Word History

Etymology

Noun

probably back-formation from foggy

First Known Use

Noun

1544, in the meaning defined at sense 1a

Verb

circa 1592, in the meaning defined at transitive sense 1

Phrases Containing fog

• brain fog
• fog lamp
• fog light
• ice fog

Rhymes for fog

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

Kids Definition

fog

1 of 2 noun

ˈfȯg 

ˈfäg

1

a

: fine particles of water floating in the atmosphere near the ground

b

: a fine spray or a foam for firefighting

2

: a gloomy condition of the atmosphere or a substance causing it

3

: a state of mental confusion

spent the morning in a fog

fog

2 of 2 verb

fogged; fogging

1

: to cover or become covered with or as if with fog

2

: to make confused

Medical Definition

fog

transitive verb

ˈfäg, ˈfȯg 

fogged; fogging

: to blur (a visual field) with lenses that prevent a sharp focus in order to relax accommodation before testing vision