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)
verb (used with object)
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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:
They feature a superlight foam cushion, springy carbon-fiber plate and titanium spikes.
From The Wall Street Journal ● Jul. 22, 2026
Busakorn also noted that the stage was decorated using highly flammable materials such as plastic flowers, while the ceiling was plastered with combustible foam.
From BBC ● Jul. 14, 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
Over the next week, the fire continued to burn through dense insulation foam within the building’s walls and other unknown industrial materials, blanketing much of L.A. in acrid smoke.
From Los Angeles Times ● Jun. 30, 2026
The feast day of Venus was, of course, especially honored in Cyprus, the island which first received the goddess after she rose from the foam.
From "Mythology: Timeless Tales of Gods and Heroes" by Edith Hamilton
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
One of the chemicals found by both the EA and the independent testing is PFOS, a substance banned in the UK due to potential carcinogenic risks, often used in firefighting foams.
From BBC ● May 20, 2026
Since then, high-tech foams have been perfected to return more energy to the runner than ever and come in lighter than previous materials.
From The Wall Street Journal ● Apr. 26, 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
Products like single-use packaging, plastic resins, foamed plastic insulation, bottles and containers, among many others, add to global greenhouse emissions.
From Washington Times ● Jul. 1, 2022
Since then, Queensland has been using a process called foamed bitumen stabilisation.
From BBC ● Feb. 10, 2022
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
First he took out his dad's shaving cream and pushed the button on top so that it foamed out into his hand.
From "All About Sam" by Lois Lowry
“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
She calmly described how her mum had been foaming at the mouth and shaking, and clearly gave their address when asked, LAS said.
From BBC ● Apr. 10, 2026
The A12 cafe, on one of the busiest avenues in the capital, displays a large picture of a foaming pint on its window.
From Barron's ● Nov. 19, 2025
Hernandez told police she found her baby foaming at the mouth and having an apparent seizure after emerging from her procedure at Always Beautiful Medical Spa, according to the police report.
From Los Angeles Times ● Jul. 9, 2025
Gogol pokes his head into the pot and sees the vongole, their shells uniformly parted in a quietly foaming broth.
From "The Namesake" by Jhumpa Lahiri
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.
