Apparently a primary word; froth, i.e. Slaver -- foaming.
Luke 9:39 - N-GMSGRK: αὐτὸν μετὰ ἀφροῦ καὶ μόγιςNAS: and it throws him into a convulsion with foaming [at the mouth]; and only with difficultyKJV: him that he foameth again,INT: him with foaming and with difficulty