foam

American  

[fohm] / foʊm /

noun

1. a collection of minute bubbles formed on the surface of a liquid by agitation, fermentation, etc..

   foam on a glass of beer.

   Synonyms:

   scum, fizz, head, spume, froth

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.

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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.

idioms

1. foam at the mouth, to be extremely or uncontrollably angry.

foam British  

/ fəʊm /

noun

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

4. 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

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

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

7. a poetic word for the sea

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verb

1. to produce or cause to produce foam; froth

2. (intr) to be very angry (esp in the phrase foam at the mouth )

foam Scientific  

/ 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.

3. Compare aerosol emulsion

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Other Word Forms

• defoam verb (used with object)
• foamable adjective
• foamer noun
• foamingly adverb
• foamless adjective
• foamlike adjective
• unfoamed adjective
• unfoaming adjective

Etymology

Origin of foam

before 900; Middle English fom, Old English fām; cognate with German Feim

Example Sentences

I always get the Andante, a cold brew with maple syrup, salted sweet cream foam, cacao powder and pink salt.

From Los Angeles Times • Apr. 3, 2026

Common insulation materials include fibreglass, non-combustible mineral wool, foam boards and natural fibre such as wood or cork.

From BBC • Mar. 25, 2026

The inferno swept through seven of the estate's eight towers, which were under renovation and wrapped in bamboo scaffolding, netting and foam boards -- materials that may have accelerated the spread of flames.

From Barron's • Mar. 24, 2026

To better understand what was happening, the researchers recorded video inside the foam.

From Science Daily • Mar. 23, 2026

Dark, choppy waves, crested with foam, were plowing across the sand.

From "Dog Squad" by Chris Grabenstein

Related Words

• cream
• froth
• spray