foam
Americannoun
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a collection of minute bubbles formed on the surface of a liquid by agitation, fermentation, etc..
foam on a glass of beer.
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the froth of perspiration, caused by great exertion, formed on the skin of a horse or other animal.
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froth formed from saliva in the mouth, as in epilepsy and rabies.
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a thick frothy substance, as shaving cream.
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(in firefighting)
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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.
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the layer of bubbles so formed.
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a dispersion of gas bubbles in a solid, as foam glass, foam rubber, polyfoam, or foamed metal.
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Literary. the sea.
verb (used without object)
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foams,
present (3rd person singular)
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foamed,
past participle, past
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foaming
present participle
verb (used with object)
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foams,
present (3rd person singular)
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foamed,
past participle, past
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foaming
present participle
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to cause to foam.
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to cover with foam; apply foam to.
to foam a runway before an emergency landing.
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to insulate with foam.
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to make (plastic, metal, etc.) into a foam.
idioms
noun
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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
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frothy saliva sometimes formed in and expelled from the mouth, as in rabies
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the frothy sweat of a horse or similar animal
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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
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( as modifier )
foam rubber
foam plastic
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a colloid consisting of a gas suspended in a liquid
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a mixture of chemicals sprayed from a fire extinguisher onto a burning substance to create a stable layer of bubbles which smothers the flames
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a poetic word for the sea
verb
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to produce or cause to produce foam; froth
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(intr) to be very angry (esp in the phrase foam at the mouth )
Other Word Forms
Derived Forms
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foamernoun
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defoamverb (used with object)
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foamableadjective
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foamlessadjective
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foamlikeadjective
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unfoamedadjective
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unfoamingadjective
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foaminglyadverb
Inflected Forms
Participles
Conjugated Forms
Present
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foamsimple
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foamssimple
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have foamedperfect
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has foamedperfect
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am foamingprogressive
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are foamingprogressive
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is foamingprogressive
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have been foamingperfect progressive
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has been foamingperfect progressive
Past
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foamedsimple
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had foamedperfect
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was foamingprogressive
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were foamingprogressive
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had been foamingperfect progressive
Future
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
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
You can then progress to standing on a folded towel or foam pad.
From Science Daily ● Aug. 16, 2026
Baidoo suggests a more supportive flip-flop, such as a FitFlop, which is sturdier and contoured - a world away from the flat and thin flip-flops that have been cut from a big sheet of foam.
From BBC ● Aug. 4, 2026
They feature a superlight foam cushion, springy carbon-fiber plate and titanium spikes.
From The Wall Street Journal ● Jul. 22, 2026
They’re from melting insulation foam and whatever it is that gets airborne when fire assails solar panels.
From Los Angeles Times ● Jul. 15, 2026
The four stallions stumbled often: thick sweat dripped from their flanks and a bloody foam dripped from their lips.
From "Stardust" by Neil Gaiman
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
Gas-injected foams and paper-thin uppers make high-tech shoes lighter than ever before—and records are tumbling just as fast.
From The Wall Street Journal ● Feb. 19, 2026
Spring fog foams over the ramparts of the newly opened Belle Isle Bridge.
From "Middlesex: A Novel" by Jeffrey Eugenides
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
It foamed and raged and swept citizens along in its wake, but Nora alone was strong enough to outjump it.
From Slate ● Aug. 28, 2021
Wind foamed the sea, rocked the boat, and whipped at their clothes as they strained to get ashore.
From "The Red Car to Hollywood" by Jennie Liu
“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
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
Symptoms of muscarine poisoning include muscle cramps, blurred vision, foaming from the mouth, vomiting and diarrhea.
From Salon ● Feb. 20, 2025
It was actually in the shallows, its feet lost in little foaming eddies that curled against the bank.
From "Strange the Dreamer" by Laini Taylor
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
