inexhaustible

showing no signs of weariness even after long hard effort seemingly inexhaustible horses that pulled heavy wagons across the wide prairies Synonyms indefatigable, tireless, unflagging, untiring, wearilessRelated Words assiduous, conscientious, diligent, meticulous, painstaking, sedulous; determined, dogged, patient, persevering, persistent, pertinacious, plodding, relentless, steadfast, steady, stubborn, tenacious, unabating, unfailing, unfaltering, unflinching, unrelenting, unremitting, unwavering; active, busy, dynamic, energetic, feverish, spirited, vigorous; hard, industrious, intense, laborious, slavish, strenuousNear Antonyms indolent, lackadaisical, laggard, lazy, listless, shiftless, slothful, sluggish; apathetic, casual, desultory, languid, spiritless; beat, broken, burned-out (or burnt-out), done in, drained, enervated, jaded, overtaxed, overworked, played out, sapped, spent, tuckered (out), wearied, worn-out