Indefatigable

a. [Prefix in, not, and defatigable; O. Fr. indéfatigable, Lat. indefatigabilis. Cf. INFATIGABLE.] Incapable of being fatigued; not readily exhausted or overcome by labor; unremitting in labor or effort; not tired; not yielding to fatigue; as, indefatigable exertions; indefatigable attendance or perseverance.

Upborne with indefatigable wings. Milton.

Synonyms— Unwearied; untiring; persevering; assiduous.