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)

• foams,
  present (3rd person singular)
• foamed,
  past participle,  past
• foaming
  present participle

1. to form or gather foam; emit foam; froth.

verb (used with object)

• foams,
  present (3rd person singular)
• foamed,
  past participle,  past
• foaming
  present participle

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

Derived Forms

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

Inflected Forms

Participles

• foaming
  present
• foamed
  past

Conjugated Forms

Present

• foam
  simple
• foams
  simple
• have foamed
  perfect
• has foamed
  perfect
• am foaming
  progressive
• are foaming
  progressive
• is foaming
  progressive
• have been foaming
  perfect progressive
• has been foaming
  perfect progressive

Past

• foamed
  simple
• had foamed
  perfect
• was foaming
  progressive
• were foaming
  progressive
• had been foaming
  perfect progressive

Future

• will foam
  simple
• will have foamed
  perfect
• will be foaming
  progressive
• will have been foaming
  perfect progressive

Etymology

Origin of foam

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

Explanation

Foam is a substance with so many tiny air bubbles that it becomes frothy or thick. Your liquid shampoo becomes a foam as you lather it into your wet hair. There's a layer of foam on top of your root beer float, and shaving cream usually comes out of its can in the form of foam. When something froths up this way, you can say that it foams, like turbulent ocean water or a bubble bath that grows as you add water to the tub. The Old English root word is fam, which means "foam," but also "saliva froth" and "sea."

Example Sentences

See Examples For:

foam foams foamed foaming

The property also features a sizable media room, an expansive primary suite—with his-and-her closets and a spalike bathroom—and a playroom with its own stage and foam pit.

From MarketWatch ● Aug. 18, 2026

You can then progress to standing on a folded towel or foam pad.

From Science Daily ● Aug. 16, 2026

Aminu said he was afraid to touch the foam but observed many others getting close to it.

From BBC ● Jul. 22, 2026

It also froths milk and makes cold foam, which opens up even more possibilities for a build-your-own drink bar.

From Salon ● Jul. 12, 2026

Cat kicked a patch of foam and watched it flutter to the sand.

From "Caterpillar Summer" by Gillian McDunn

The three movements include “an invocation to hands that weave”; “a meeting of foams, needles, songs, threats and pulsations”; and what Negrón calls “an archipelago of resonances and possibilities.”

From Los Angeles Times ● Jun. 3, 2026

The company said the Department of Defence kept using the PFAS-containing firefighting foams for two decades after it stopped selling the product in Australia.

From BBC ● May 28, 2026

They placed these foams between transparent plates and positioned them upright, allowing them to directly observe how liquid moved inside.

From Science Daily ● Mar. 23, 2026

Researchers at Tokyo Metropolitan University have uncovered the real reason liquid drains from foams, resolving a long-standing scientific puzzle.

From Science Daily ● Mar. 23, 2026

Bile foams in my gut and my thoughts tumble every which way as I try to work out how I’m going to fit a dog into my already too-jam-packed life.

From "Red Flags and Butterflies" by Sheryl Azzam

The straw made from foamed CDA was a prototype to see if increasing the surface area would accelerate break down.

From Science Daily ● Jan. 30, 2024

Also banned are disposable cups and takeaway food containers made of expanded or foamed extruded polystyrene.

From BBC ● Oct. 29, 2023

Pennsylvania officials will use 2,000 tons of lightweight foamed glass nuggets to fill in the section of a U.S.

From Washington Times ● Jun. 15, 2023

A tuft of foamed milk completes the steaming comfort.

From Washington Post ● Jan. 28, 2022

Milo’s office was a barbershop, and his deputy mayor was a pudgy barber from whose obsequious lips cordial greetings foamed as effusively as the lather he began whipping up in Milo’s shaving cup.

From "Catch-22" by Joseph Heller

“There are contestants that become very polarizing and you’ll have people absolutely foaming at the mouth wanting them to lose,” says former champion Mattea Roach, speaking from experience.

From The Wall Street Journal ● Apr. 21, 2026

Initial findings from the investigation into the blaze suggest that it was caused by sparklers igniting soundproof foaming that lined the ceiling.

From BBC ● Jan. 15, 2026

I’m not foaming at the mouth over the death of cinema or what have you.

From Los Angeles Times ● Jan. 9, 2026

They frequently contain colors, flavor enhancers, sweeteners, thickeners, foaming agents and emulsifiers, and typically cannot be produced in the home.

From Barron's ● Dec. 2, 2025

Southward he looked, and below his very feet the Great River curled like a toppling wave and plunged over the falls of Rauros into a foaming pit; a glimmering rainbow played upon the fume.

From "The Fellowship of the Ring" by J.R.R. Tolkien

Related Words

• cream
• froth
• spray