ardent, assiduous, diligent, drudging, energetic, fervent, grinding, grubbing, hard, indefatigable, industrious, laboring, laborious, never idle, pegging, plodding, plugging, relentless, sedulous, slaving, sleepless, slogging, straining, strenuous, striving, struggling, sweating, tireless, toiling, unflagging, unremitting, unsleeping, unsparing, unwearied, vehement, working, zealous