vultus

Vultus, vultus, m., fourth declension; an older neuter vultum turns up in early Latin and in poetry, and the plural vultus is often used for a single face.

It is not a synonym for facies. Facies is the face as a physical object, the front of the head; vultus is the face as it shows something, so "countenance" or "expression" is nearly always the better English. That is why the idioms are all about control: vultum fingere, to compose one's features, bono vultu, with a good grace, vultum demittere, to look down. Spelling swings between voltus and vultus in older texts and in this corpus, the u being the later habit. Italian volto continues it; English has no direct heir.