Indefatigable(a.) Incapable of being fatigued; not readily exhausted; unremitting in labor or effort; untiring; unwearyingly; not yielding to fatigue; as, indefatigable exertions, perseverance, application.
Thesaurus Entries
abiding, ardent, assiduous, constant, continuing, continuous, determined, diligent, dogged, enduring, energetic, faithful, fervent, hard, hardworking, immutable, inalterable, indomitable, industrious, inexhaustible, insistent, invincible, laborious, lasting, loyal, never idle, never-tiring, obstinate, painstaking, patient, patient as Job, permanent, perseverant, persevering, persistent, persisting, pertinacious, plodding, plugging, preoccupied, rapt, relentless, remaining, resolute, sedulous, single-minded, sleepless, slogging, stable, staying, steadfast, steady, sticking, strenuous, stubborn, sustained, tenacious, tireless, unabating, unceasing, unconquerable, undaunted, undiscouraged, undrooping, undying, unfailing, unfaltering, unflagging, unflinching, unintermitting, uninterrupted, unnodding, unrelaxing, unrelenting, unremitting, unsleeping, unsparing, unswerving, untiring, unwavering, unwearied, unwearying, unwinking, utterly attentive, vehement, vigorous, weariless, zealous