verb (used without object)

to form or gather foam; emit foam; froth.

verb (used with object)


    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. 2019

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
(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 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

foam at the mouth in Science



Small, frothy bubbles formed in or on the surface of a liquid, as from fermentation or shaking.
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.

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 Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.