1. a collection of minute bubbles formed on the surface of a liquid by agitation, fermentation, etc.: foam on a glass of beer.
  2. the froth of perspiration, caused by great exertion, formed on the skin of a horse or other animal.
  3. froth formed from saliva in the mouth, as in epilepsy and rabies.
  4. a thick frothy substance, as shaving cream.
  5. (in firefighting)
    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.
  6. a dispersion of gas bubbles in a solid, as foam glass, foam rubber, polyfoam, or foamed metal.
  7. Literary. the sea.
verb (used without object)
  1. to form or gather foam; emit foam; froth.
verb (used with object)
  1. to cause to foam.
  2. to cover with foam; apply foam to: to foam a runway before an emergency landing.
  3. to insulate with foam.
  4. to make (plastic, metal, etc.) into a foam.
  1. 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 formsfoam·a·ble, adjectivefoam·er, nounfoam·ing·ly, adverbfoam·less, adjectivefoam·like, adjectivede·foam, verb (used with object)un·foamed, adjectiveun·foam·ing, adjective

Synonyms for foam Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for foaming

Contemporary Examples of foaming

Historical Examples of foaming

British Dictionary definitions for foaming


  1. 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
  2. frothy saliva sometimes formed in and expelled from the mouth, as in rabies
  3. 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
  4. a colloid consisting of a gas suspended in a liquid
  5. a mixture of chemicals sprayed from a fire extinguisher onto a burning substance to create a stable layer of bubbles which smothers the flames
  6. a poetic word for the sea
  1. to produce or cause to produce foam; froth
  2. (intr) to be very angry (esp in the phrase foam at the mouth)
Derived Formsfoamless, adjectivefoamlike, adjective

Word Origin for foam

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

Word Origin and History for foaming



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

foaming 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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.