Indomitable, a.
Etymology: [L. indomitabilis; pref. in- not + domitare, intens. fr. domare to tame. See Tame.]
Not to be subdued; untamable; invincible; as, an indomitable will, courage, animal.
Shades of meaning
Fernald has no entry of its own for indomitable; he lists it under obstinate.
He lists it without comment; the entries above explain its neighbors.