n.1. A colloidal dispersion of a gas in a liquid or solid medium, such as shaving cream, foam rubber, or a substance used to fight fires. A foam may be produced, especially on the surface of a liquid, by agitation or by a chemical reaction, such as fermentation.
2. Any of various light, porous, semirigid or spongy materials, usually the solidified form of a liquid full of gas bubbles, used as a building material or for thermal insulation or shock absorption, as in packaging.
3. a. Frothy saliva produced especially as a result of physical exertion or a pathological condition.
b. The frothy sweat of a horse or other equine animal.
4. The sea.
v.intr.1. To produce or issue as foam; froth.
2. a. To produce foam from the mouth, as from exertion or a pathological condition.
b. To be extremely angry; rage: was foaming over the disastrous budget cuts.
3. To teem; seethe: a playground foaming with third graders.