Inhuman, a.
Etymology: [L. inhumanus: cf. F. inhumain. See In- not, and Human.]
1. Destitute of the kindness and tenderness that belong to a human being; cruel; barbarous; savage; unfeeling; as, an inhuman person or people.
2. Characterized by, or attended with, cruelty; as, an inhuman act or punishment.
Syn. -- Cruel; unfeeling; pitiless; merciless; savage; barbarous; brutal; ferocious; ruthless; fiendish.
Shades of meaning
Fernald has no entry of its own for inhuman; he lists it under barbarous.
He lists it without comment; the entries above explain its neighbors.