A substance composed of a large collection of bubbles or their solidified remains.

“He doesn't like so much foam in his beer.”

A substance formed by trapping pockets of gas in a liquid or solid.

“A foam mat can soften a hard seat.”

(by extension) Sea foam; the sea.

“He is in Europe, across the foam.”

To form or emit foam.

To spew saliva as foam, to foam at the mouth.