(a.) Untiring; indefatigable; as, a tireless worker\.

active ardent assiduous constant continuing determined diligent dogged dynamic enduring energetic enthusiastic faithful fervent hard hardworking immutable inalterable indefatigable indomitable industrious inexhaustible insistent invincible laborious lasting lively loyal never idle never-tiring obstinate patient patient as Job permanent perseverant persevering persistent persisting pertinacious plodding plugging preoccupied rapt relentless resolute sagging sedulous single-minded sleepless slogging spirited stable staunch steadfast steady strenuous stubborn tenacious unabating unconquerable undaunted undeviating undiscouraged undrooping unfailing unfaltering unflagging unflinching unintermitting uninterrupted unnodding unrelaxing unrelenting unremitting unsleeping unsparing unswerving untiring unwavering unwearied unwearying unwinking utterly attentive vehement vigorous vital weariless zealous