fog

¹ American  

[fog, fawg] / fɒg, fɔg /

noun

1. a cloudlike mass or layer of minute water droplets or ice crystals near the surface of the earth, appreciably reducing visibility.

2. any darkened state of the atmosphere, or the diffused substance that causes it.

3. a state of mental confusion or unawareness; daze; stupor.

   The survivors were in a fog for days after the catastrophe.

   Synonyms:

   dim, darken, blur, cloud, trance, muddle, haze

   Antonyms:

   clarity

4. Photography. a hazy effect on a developed negative or positive, caused by light other than that forming the image, by improper handling during development, or by the use of excessively old film.

5. Physical Chemistry. a mixture consisting of liquid particles dispersed in a gaseous medium.

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verb (used with object)

fogs, present (3rd person singular) fogged, past participle, past fogging present participle

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

   The steam in the room fogged his glasses.

2. to confuse or obscure.

   The debate did little else but fog the issue.

   Synonyms:

   obfuscate, obscure, muddy, confuse, befog, becloud

   Antonyms:

   clarify

3. to bewilder or perplex.

   to fog the mind.

   Synonyms:

   befuddle, daze, mystify, muddle

4. Photography. to produce fog on (a negative or positive).

verb (used without object)

fogs, present (3rd person singular) fogged, past participle, past fogging present participle

1. to become enveloped or obscured with or as if with fog.

   Antonyms:

   clear

2. Photography. (of a negative or positive) to become affected by fog.

fog ² American  

[fog, fawg] / fɒg, fɔg /

noun

U.S. and British Dialect.

1. a second growth of grass, as after mowing.

2. long grass left standing in fields during the winter.

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fog ¹ British  

/ fɒɡ /

noun

1. a mass of droplets of condensed water vapour suspended in the air, often greatly reducing visibility, corresponding to a cloud but at a lower level

2. a cloud of any substance in the atmosphere reducing visibility

3. a state of mental uncertainty or obscurity

4. photog a blurred or discoloured area on a developed negative, print, or transparency caused by the action of extraneous light, incorrect development, etc

5. a colloid or suspension consisting of liquid particles dispersed in a gas

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verb

1. to envelop or become enveloped with or as if with fog

2. to confuse or become confused

   to fog an issue

3. photog to produce fog on (a negative, print, or transparency) or (of a negative, print, or transparency) to be affected by fog

fog ² British  

/ fɒɡ /

noun

1. 1. a second growth of grass after the first mowing

   2. grass left to grow long in winter

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fog Scientific  

/ fôg /

1. A dense layer of cloud lying close to the surface of the ground or water and reducing visibility to less than 1 km (0.62 mi). Fog occurs when the air temperature becomes identical, or nearly identical, to the dew point.

2. An opaque or semiopaque condensation of a substance floating in a region or forming on a surface.

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fog Idioms  

1. see in a fog.

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Synonym Usage

See cloud.

Other Word Forms

Derived Forms

• unfogging
  adjective
• fogless
  adjective
• unfogged
  adjective

Conjugated Forms

Present

• has fogged
  perfect 3rd person singular
• have fogged
  perfect
• has been fogging
  perfect progressive 3rd person singular
• are fogging
  progressive
• fogging
  participle
• have been fogging
  perfect progressive
• is fogging
  progressive 3rd person singular
• am fogging
  progressive 1st person singular
• fogs
  singular 3rd person

Past

• had fogged
  perfect
• were fogging
  progressive plural
• had been fogging
  perfect progressive
• fogged
  participle
• was fogging
  progressive singular
• fogged
  simple

Future

• will fog
  simple
• will have fogged
  perfect
• will be fogging
  progressive
• will have been fogging
  perfect progressive

Etymology

Origin of fog¹

First recorded in 1535–45; perhaps by back formation from foggy; see fog ²

Origin of fog²

First recorded in 1300–50; Middle English fogge, from Scandinavian; compare Norwegian fogg “long, scattered grass on damp ground”; further origin uncertain; see also foggy

Explanation

Fog is a hazy, cloudy layer of water vapor very that hovers close to the ground. Driving in fog feels a bit like being inside a cloud. Fog is just what it appears to be — a cloud lying low in the atmosphere, getting its moisture from a body of water like the ocean or a river. When fog is thick, it can be dangerous to drive in, and most cars have special "fog lights" to help drivers see the road. When you're deeply confused, you can call it a fog too, and when things are unclear (literally or figuratively), they're said to fog up."

Example Sentences

Warsh’s confirmation testimony cut through the fog: inflation is not an act of God, a shipping-container mystery, or a Gulf headline.

From MarketWatch • Jun. 6, 2026

“The fog around tariff-regime uncertainty is finally lifting, and the proposed rates carry little shock value,” he said.

From Barron's • Jun. 3, 2026

Another possibility is that the clouds evaporate as they move into temperatures exceeding 1,000 degrees, similar to morning fog burning away on Earth but under far more extreme conditions.

From Science Daily • May 27, 2026

Onto the rest: “Maid of Honour” calls back to his failed-but-intriguing experiment in deep house, 2022’s “Honestly, Nevermind,” but subs out that LP’s raver fog for squelchy Miami bass, footwork and ghettotech.

From Los Angeles Times • May 15, 2026

The moon lights a layer of fog on the lake.

From "The Bletchley Riddle" by Ruta Sepetys and Steve Sheinkin

Related Words

• cloud
• gloom
• smog
• smoke
• steam
• vapor