INDOMITABLE
indomitable, never-say-die, unsubduable
(adjective) impossible to subdue
Source: WordNet® 3.1
Etymology
Adjective
indomitable (comparative more indomitable, superlative most indomitable)
Incapable of being subdued, overcome, or vanquished.
Synonyms
• See Thesaurus:indomitable
Source: Wiktionary
In*dom"i*ta*ble, a. Etym: [L. indomitabilis; pref. in- not +
domitare, intens. fr. domare to tame. See Tame.]
Definition: Not to be subdued; untamable; invincible; as, an indomitable
will, courage, animal.
Source: Webster’s Unabridged Dictionary 1913 Edition