Synonyms for Tireless (same or very similar meaning)
WordNet sense 1 (showing sustained enthusiastic action with unflagging vitality):
indefatigable, unflagging, unwearyingWordNet sense 2 (possessing or exerting or displaying energy):
energeticWordNet sense 3 (characterized by hard work and perseverance):
hardworking, industrious, untiringFrom the ODE community, based on WordNetadd/edit