Indomitable means impossible to defeat or discourage. Whatever happens, they get up again.
It is high praise and it usually attaches to spirit, will or a person, so an indomitable spirit is close to a fixed phrase and it appears in a great many obituaries. The Latin root means untameable, which is exactly the flavour. It suits people who have had a very hard time and kept going. Unconquerable and invincible are its neighbours, and invincible is about power rather than character.
1adjectiveindomitableImpossible to subdue or discourage.
“She had an indomitable will right to the end.”
Indomitable cannot be tamed. Latin in, not, joins domō, to tame, so the word says of a person that nobody has ever broken them in.
Proto-Indo-European
*demh₂-
Latin
indomitābilis
English, today
indomitable
Built from
From Latin indomitābilis, from in- (“not”) + domitō, frequentative of domō (“to tame”). by surface analysis, in- + domitable.
Etymology from Wiktionary, CC BY-SA