[ fohm ]
See synonyms for: foamfoaming on

  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.

  1. froth formed from saliva in the mouth, as in epilepsy and rabies.

  2. a thick frothy substance, as shaving cream.

  3. (in firefighting)

    • 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.

    • the layer of bubbles so formed.

  4. a dispersion of gas bubbles in a solid, as foam glass, foam rubber, polyfoam, or foamed metal.

  5. 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.

  1. to insulate with foam.

  2. to make (plastic, metal, etc.) into a foam.

Idioms about 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

Other words for foam

Other words from foam

  • foam·a·ble, adjective
  • foamer, noun
  • foam·ing·ly, adverb
  • foamless, adjective
  • foamlike, adjective
  • de·foam, verb (used with object)
  • un·foamed, adjective
  • un·foam·ing, adjective

Words Nearby foam Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use foam in a sentence

British Dictionary definitions for foam


/ (fəʊm) /

  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

  1. the frothy sweat of a horse or similar animal

    • 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

    • (as modifier): foam rubber; foam plastic

  2. a colloid consisting of a gas suspended in a liquid

  3. a mixture of chemicals sprayed from a fire extinguisher onto a burning substance to create a stable layer of bubbles which smothers the flames

  4. 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)

Origin of foam

Old English fām; related to Old High German feim, Latin spūma, Sanskrit phena

Derived forms of foam

  • foamless, adjective
  • foamlike, adjective

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

Scientific definitions for foam


[ fōm ]

  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.