Definition of foam noun from the Oxford Advanced Learner's Dictionary

foam

noun
fəʊm
 
; foʊm
 
 
1 (also foam rubber) [uncountable] a soft light rubber material, full of small holes, that is used for seats, mattresses, etca foam mattressfoam packaging2 [uncountable] a mass of very small air bubbles on the surface of a liquid
Synonym
froth
a glass of beer with a good head of foamThe breaking waves left the beach covered with foam.
3 [uncountable, countable] a chemical substance that forms or produces a soft mass of very small bubbles, used for washing, shaving, or putting out fires, for exampleshaving foama bottle of bath foamThe fire extinguisher directs foam onto the fire.