foam

n. light frothy mass of bubbles; spongy material (used in upholstery)

v. froth, produce or form a light frothy mass of bubbles; cause to foam

The most general definition of foam is a substance that is formed by trapping many gas bubbles in a liquid or solid. It can also refer to anything that is analogous to such a phenomenon, such as quantum foam. Often people mean polyurethane foam (foam rubber), Styrofoam or some other manufactured foam when they are using the term. It can be considered a type of colloid.
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Foam 1. a dispersion of a gas in a liquid or solid. 2. frothy saliva. 3. to produce or cause production of such a substance. [more]Foam - Community and Resources

Noun
1. a mass of small bubbles formed in or on a liquid
(synonym) froth
(hypernym) bubble
(hyponym) shaving foam
(derivation) froth, fizz, effervesce, sparkle
2. a lightweight material in cellular form; made by introducing gas bubbles during manufacture
(hypernym) material, stuff
(hyponym) Styrofoam
Verb
1. form bubbles; "The boiling soup was frothing"; "The river was foaming"; "Sparkling water"
(synonym) froth, fizz, effervesce, sparkle
(hypernym) bubble
(hyponym) lather
(derivation) froth

Compare with colloid .A colloid in which bubbles of gas are suspended in a solid or liquid. Aerogel (solid smoke) and Styrafoam are examples of solid foams; whipped cream is an example of a liquid foam.