[ fog, fawg ]
See synonyms for fog on
  1. a cloudlike mass or layer of minute water droplets or ice crystals near the surface of the earth, appreciably reducing visibility.: Compare ice fog, mist (def. 1), smog (def. 1).

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

  1. a state of mental confusion or unawareness; daze; stupor: The survivors were in a fog for days after the catastrophe.

  2. 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.

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

verb (used with object),fogged, fog·ging.
  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.

  1. to bewilder or perplex: to fog the mind.

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

verb (used without object),fogged, fog·ging.
  1. to become enveloped or obscured with or as if with fog.

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

Origin of fog

First recorded in 1535–45; perhaps by back formation from foggy; see fog2

synonym study For fog

3. See cloud.

Other words for fog

Opposites for fog

Other words from fog

  • fogless, adjective
  • un·fogged, adjective
  • un·fog·ging, adjective

Other definitions for fog (2 of 2)

[ fog, fawg ]

nounU.S. and British Dialect.
  1. a second growth of grass, as after mowing.

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

Origin of fog

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 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use fog in a sentence

  • The damp air was fogging the lenses, but I kept them to my eyes; for I did not want to look at Davies.

    The Riddle of the Sands | Erskine Childers
  • He wasn't a man to follow problems to a conclusion, however, and it simply hung in his mind as a fogging event.

    The Three Sapphires | W. A. Fraser
  • Photographers must know that fogging and blurring the image is curtailing the experience of it.

    Adventures in the Arts | Marsden Hartley
  • He is none the less magic because he works through one great spell, and not through a host of minor, petti-fogging miracles.

    God and Mr. Wells | William Archer
  • Of all developers it is most free from fogging propensities.

British Dictionary definitions for fog (1 of 2)


/ (fɒɡ) /

  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

  1. a state of mental uncertainty or obscurity

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

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

verbfogs, fogging or fogged
  1. to envelop or become enveloped with or as if with fog

  2. to confuse or become confused: to fog an issue

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

Origin of fog

C16: perhaps back formation from foggy damp, boggy, from fog ²

British Dictionary definitions for fog (2 of 2)


/ (fɒɡ) /

    • a second growth of grass after the first mowing

    • grass left to grow long in winter

Origin of fog

C14: probably of Scandinavian origin; compare Norwegian fogg rank grass

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for fog


[ 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.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Other Idioms and Phrases with fog


see in a fog.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.