(a.) Not to be subdued; unconquerable; untamable; as, indomitable courage\.

assiduous beyond control brave breachy constant continuing contumacious courageous dauntless defiant determined diligent dogged enduring faithful fearless fractious immutable impassable impenetrable impregnable inalterable incontestable incorrigible indefatigable indocile industrious inexpugnable insistent insuperable insuppressible insurmountable intractable intrepid invincible inviolable invulnerable irrepressible irresistible lasting loyal mettlesome never-tiring obstinate obstreperous out of hand overpowering overwhelming patient patient as Job permanent perseverant persevering persistent persisting pertinacious plodding plucky plugging preoccupied rapt recalcitrant refractory relentless resistant resisting resistless resolute resolved restive sedulous shrewish single-minded sleepless slogging stable staunch steadfast steady stubborn tenacious tireless unabating unafraid unassailable unbeatable unbiddable unconquerable uncontrollable undaunted undefeatable undisciplined undiscouraged undrooping unfailing unfaltering unflagging unflinching ungovernable unintermitting uninterrupted unmalleable unmanageable unmoldable unnodding unrelaxing unrelenting unremitting unruly unsleeping unstoppable unsubduable unsubmissive unsurmountable unswerving untiring unwavering unwearied unwearying unwinking unyielding utterly attentive weariless wild