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[fohm] /foʊm/
a collection of minute bubbles formed on the surface of a liquid by agitation, fermentation, etc.:
foam on a glass of beer.
the froth of perspiration, caused by great exertion, formed on the skin of a horse or other animal.
froth formed from saliva in the mouth, as in epilepsy and rabies.
a thick frothy substance, as shaving cream.
  1. a chemically produced substance that smothers the flames on a burning liquid by forming a layer of minute, stable, heat-resistant bubbles on the liquid's surface.
  2. the layer of bubbles so formed.
a dispersion of gas bubbles in a solid, as foam glass, foam rubber, polyfoam, or foamed metal.
Literary. the sea.
verb (used without object)
to form or gather foam; emit foam; froth.
verb (used with object)
to cause to foam.
to cover with foam; apply foam to:
to foam a runway before an emergency landing.
to insulate with foam.
to make (plastic, metal, etc.) into a foam.
foam at the mouth, to be extremely or uncontrollably angry.
Origin of foam
before 900; Middle English fom, Old English fām; cognate with German Feim
Related forms
foamable, adjective
foamer, noun
foamingly, adverb
foamless, adjective
foamlike, adjective
defoam, verb (used with object)
unfoamed, adjective
unfoaming, adjective
1. froth, spume, head, fizz; scum. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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British Dictionary definitions for foam at the mouth


a mass of small bubbles of gas formed on the surface of a liquid, such as the froth produced by agitating a solution of soap or detergent in water
frothy saliva sometimes formed in and expelled from the mouth, as in rabies
the frothy sweat of a horse or similar animal
  1. any of a number of light cellular solids made by creating bubbles of gas in the liquid material and solidifying it: used as insulators and in packaging
  2. (as modifier): foam rubber, foam plastic
a colloid consisting of a gas suspended in a liquid
a mixture of chemicals sprayed from a fire extinguisher onto a burning substance to create a stable layer of bubbles which smothers the flames
a poetic word for the sea
to produce or cause to produce foam; froth
(intransitive) to be very angry (esp in the phrase foam at the mouth)
Derived Forms
foamless, adjective
foamlike, adjective
Word Origin
Old English fām; related to Old High German feim, Latin spūma, Sanskrit phena
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
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Word Origin and History for foam at the mouth



Old English fam "foam, saliva froth," from West Germanic *faimo- (cf. Old High German veim, German Feim), from PIE *(s)poi-mo-, a root with connotations of "foam, froth" (cf. Sanskrit phenah; Latin pumex "pumice," spuma "foam;" Old Church Slavonic pena "foam;" Lithuanian spaine "a streak of foam"). The rubber or plastic variety so called from 1937.


Old English famgian "to foam," from the source of foam (n.). Related: Foamed; foaming.

Online Etymology Dictionary, © 2010 Douglas Harper
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foam at the mouth in Science
  1. Small, frothy bubbles formed in or on the surface of a liquid, as from fermentation or shaking.

  2. A colloid in which particles of a gas are dispersed throughout a liquid. Compare aerosol, emulsion.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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foam at the mouth in the Bible

(Hos. 10:7), the rendering of _ketseph_, which properly means twigs or splinters (as rendered in the LXX. and marg. R.V.). The expression in Hosea may therefore be read, "as a chip on the face of the water," denoting the helplessness of the piece of wood as compared with the irresistable current.

Easton's 1897 Bible Dictionary
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Idioms and Phrases with foam at the mouth

foam at the mouth

Be extremely angry, as in She was foaming at the mouth over the judge's ruling. This hyperbolic term uses the verb foam in the sense of “froth at the mouth,” a usage generally applied to animals such as horses and dating from about a.d. 950. [ 1400s ]
The American Heritage® Idioms Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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