a collection of minute bubbles formed on the surface of a liquid by agitation, fermentation, etc.: foam on a glass of beer.
the froth of perspiration, caused by great exertion, formed on the skin of a horse or other animal.
froth formed from saliva in the mouth, as in epilepsy and rabies.
a thick frothy substance, as shaving cream.
(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.
a dispersion of gas bubbles in a solid, as foam glass, foam rubber, polyfoam, or foamed metal.
Literary. the sea.
verb (used without object)
to form or gather foam; emit foam; froth.
verb (used with object)
to cause to foam.
to cover with foam; apply foam to: to foam a runway before an emergency landing.
to insulate with foam.
to make (plastic, metal, etc.) into a foam.
Idioms
foam at the mouth, to be extremely or uncontrollably angry.
Origin of foam
before 900;Middle Englishfom,Old Englishfām; cognate with GermanFeim
Related formsfoam·a·ble, adjectivefoam·er, nounfoam·ing·ly, adverbfoam·less, adjectivefoam·like, adjectivede·foam, verb (used with object)un·foamed, adjectiveun·foam·ing, adjective
British Dictionary definitions for foam at the mouth
foam
noun
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
frothy saliva sometimes formed in and expelled from the mouth, as in rabies
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
a colloid consisting of a gas suspended in a liquid
a mixture of chemicals sprayed from a fire extinguisher onto a burning substance to create a stable layer of bubbles which smothers the flames
Old English fam "foam, saliva froth," from West Germanic *faimo- (cf. Old High German veim, German Feim), from PIE *(s)poi-mo-, a root with connotations of "foam, froth" (cf. Sanskrit phenah; Latin pumex "pumice," spuma "foam;" Old Church Slavonic pena "foam;" Lithuanian spaine "a streak of foam"). The rubber or plastic variety so called from 1937.
foam
v.
Old English famgian "to foam," from the source of foam (n.). Related: Foamed; foaming.
Be extremely angry, as in She was foaming at the mouth over the judge's ruling. This hyperbolic term uses the verb foam in the sense of “froth at the mouth,” a usage generally applied to animals such as horses and dating from about a.d. 950. [1400s]
