From Longman Dictionary of Contemporary Englishindomitablein‧dom‧i‧ta‧ble /ɪnˈdɒmətəbəl $ ɪnˈdɑː-/ adjective formal BRAVEhaving great determination or courage an indomitable old ladyindomitable spirit/will/courage etc Alice was a woman of indomitable spirit.
Examples from the Corpus
indomitable• an indomitable will to succeedindomitable spirit/will/courage etc• Alice Fernie was a woman of indomitable spirit.• Her indomitable spirit is testament enough to her working class, Liverpudlian roots.• None of his victories was more characteristic of his indomitable will to win than his first success in the Arlington Million.• The chief inspector suddenly understood that the historian's self-important but indomitable spirit was housed in a broken body.Origin indomitable (1600-1700) Late Latin indomitabilis, from Latin domitare “to control the behavior of” 