Pronunciation: (fōm),[key] —n. 1. a collection of minute bubbles formed on the surface of a liquid by agitation, fermentation, etc.: foam on a glass of beer. 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)
a. 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.
b. 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.
—v.i. to form or gather foam; emit foam; froth.
—v.t. 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.
5. foam at the mouth, to be extremely or uncontrollably angry.