Foam, v. i. [imp. & p. p.Foamed (fōmd); p. pr. & vb. n.Foaming.] [AS. f?man. See Foam, n.] 1. To gather foam; to froth; as, the billows foam.
He foameth, and gnasheth with his teeth. Mark ix. 18.
2. To form foam, or become filled with foam; — said of a steam boiler when the water is unduly agitated and frothy, as because of chemical action.