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, smog.
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.
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.
–verb (used with object)
6.
to cover or envelop with or as if with fog: The steam in the room fogged his glasses.
7.
to confuse or obscure: The debate did little else but fog the issue.
8.
to bewilder or perplex: to fog the mind.
9.
Photography. to produce fog on (a negative or positive).
–verb (used without object)
10.
to become enveloped or obscured with or as if with fog.
11.
Photography. (of a negative or positive) to become affected by fog.
[Origin: 1535–45; perh. by back formation from foggy.See fog2]
1544, from Dan. fog "spray, shower, snowdrift," related to O.N. fok "snow flurry." The word meaning "long grass" (c.1300) may be a different word, but the two may connect via a notion of long grass growing in moist dells of northern Europe. Phrase in a fog "at a loss what to do" first recorded 1602. Foggy Bottom "U.S. Department of State," from the name of a marshy region of Washington, D.C., where many federal buildings are (also with a punning allusion to political murkiness) popularized 1947 by James Reston in "New York Times," but he said it had been used earlier by Edward Folliard of "The Washington Post."
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.
An opaque or semiopaque condensation of a substance floating in a region or forming on a surface.
Cloud\ (kloud), n. [Prob. fr. AS. cl[=u]d a rock or hillock, the application arising from the frequent resemblance of clouds to rocks or hillocks in the sky or air.]1. A collection of visible vapor, or watery particles, suspended in the upper atmosphere. I do set my bow in the cloud. --Gen. ix. 13. Note: A classification of clouds according to their chief forms was first proposed by the meteorologist Howard, and this is still substantially employed. The following varieties and subvarieties are recognized: (a) Cirrus. This is the most elevated of all the forms of clouds; is thin, long-drawn, sometimes looking like carded wool or hair, sometimes like a brush or room, sometimes in curl-like or fleecelike patches. It is the cat's-tail of the sailor, and the mare's-tail of the landsman. (b) Cumulus. This form appears in large masses of a hemispherical form, or nearly so, above, but flat below, one often piled above another, forming great clouds, common in the summer, and presenting the appearance of gigantic mountains crowned with snow. It often affords rain and thunder gusts. (c) Stratus. This form appears in layers or bands extending horizontally. (d) Nimbus. This form is characterized by its uniform gray tint and ragged edges; it covers the sky in seasons of continued rain, as in easterly storms, and is the proper rain cloud. The name is sometimes used to denote a raining cumulus, or cumulostratus. (e) Cirro-cumulus. This form consists, like the cirrus, of thin, broken, fleecelice clouds, but the parts are more or less rounded and regulary grouped. It is popularly called mackerel sky. (f) Cirro-stratus. In this form the patches of cirrus coalesce in long strata, between cirrus and stratus. (g) Cumulo-stratus. A form between cumulus and stratus, often assuming at the horizon a black or bluish tint. -- Fog, cloud, motionless, or nearly so, lying near or in contact with the earth's surface. -- Storm scud, cloud lying quite low, without form, and driven rapidly with the wind. 2. A mass or volume of smoke, or flying dust, resembling vapor. "A thick cloud of incense." --Ezek. viii. 11. 3. A dark vein or spot on a lighter material, as in marble; hence, a blemish or defect; as, a cloud upon one's reputation; a cloud on a title. 4. That which has a dark, lowering, or threatening aspect; that which temporarily overshadows, obscures, or depresses; as, a cloud of sorrow; a cloud of war; a cloud upon the intellect. 5. A great crowd or multitude; a vast collection. "So great a cloud of witnesses." --Heb. xii. 1. 6. A large, loosely-knitted scarf, worn by women about the head. Cloud on a (or the) title (Law), a defect of title, usually superficial and capable of removal by release, decision in equity, or legislation. To be under a cloud, to be under suspicion or in disgrace; to be in disfavor. In the clouds, in the realm of facy and imagination; beyond reason; visionary.
Fog\ (f[o^]g), n. [Cf. Scot. fog, fouge, moss, foggage rank grass, LL. fogagium, W. ffwg dry grass.] (Agric.) (a) A second growth of grass; aftergrass. (b) Dead or decaying grass remaining on land through the winter; -- called also foggage. [Prov.Eng.] --Halliwell. Note: Sometimes called, in New England, old tore. In Scotland, fog is a general name for moss.
Fog\ n. [Dan. sneefog snow falling thick, drift of snow, driving snow, cf. Icel. fok spray, snowdrift, fj[=u]k snowstorm, fj[=u]ka to drift.]1. Watery vapor condensed in the lower part of the atmosphere and disturbing its transparency. It differs from cloud only in being near the ground, and from mist in not approaching so nearly to fine rain. See Cloud. 2. A state of mental confusion. Fog alarm, Fog bell, Fog horn, etc., a bell, horn, whistle or other contrivance that sounds an alarm, often automatically, near places of danger where visible signals would be hidden in thick weather. Fog bank, a mass of fog resting upon the sea, and resembling distant land. Fog ring, a bank of fog arranged in a circular form, -- often seen on the coast of Newfoundland.
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Audio Help [fog, fawg] Pronunciation Key noun, verb, fogged, fog·ging. 
- in Indo-European roots.]
