1 (also foam rubber) [U] a soft light rubber material, full of small holes, that is used for seats, MATTRESSES, etc:
a foam mattress * foam packaging
2 [U] a mass of very small air bubbles on the surface of a liquid:
a glass of beer with a good head of foam * The breaking waves left the beach covered with foam.
3 [U,C] a chemical substance that forms or produces a soft mass of very small bubbles, used for washing, shaving, or putting out fires, for example:
shaving foam * a bottle of bath foam * The fire extinguisher directs foam onto the fire.
verb [V] (of a liquid) to have or produce a mass of small bubbles
SYNFROTH:
She looked down at the foaming white water. * The toothpaste foamed in his mouth. * tankards of foaming beer
IDIOMS
foam at the mouth
1 (especially of an animal) to have a mass of small bubbles in and around its mouth, especially because it is ill or angry
2 (informal) (of a person) to be very angry
