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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.
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. 2015.
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British Dictionary definitions for defoam


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 defoam



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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defoam 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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defoam 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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Encyclopedia Article for defoam


in physical chemistry, a colloidal system (i.e., a dispersion of particles in a continuous medium) in which the particles are gas bubbles and the medium is a liquid. The term also is applied to material in a lightweight cellular spongy or rigid form. Liquid foams are sometimes made relatively long-lasting-e.g., for fire fighting-by adding some substance, called a stabilizer, that prevents or retards the coalescence of the gas bubbles. Of the great variety of substances that act as foam stabilizers, the best known are soaps, detergents, and proteins. Proteins, because they are edible, find wide use as foaming agents in foodstuffs such as whipped cream, marshmallow (made from gelatin and sugar), and meringue (from egg white). The foam used to combat oil fires consists of bubbles of carbon dioxide (liberated from sodium bicarbonate and aluminum sulfate) stabilized by dried blood, glue, or other cheap protein-containing materials. Beer foam is believed to be stabilized by the colloidal constituents present, which include proteins and carbohydrates. Foaming may be undesirable, as in lubricating oils, and its prevention is not always easy. Aqueous foams usually can be broken by treatment with small amounts of certain alcohols.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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