indefatigable

Having or showing a capacity for persistent effort; not tiring or relenting: synonym: tireless.

Not defatigable; incapable of being fatigued; not easily exhausted; not yielding to fatigue; unremitting in labor or effort.

Synonyms Unwearied, untiring, tireless, unflagging, persevering, assiduous, persistent, sedulous.

Incapable of being fatigued; not readily exhausted; unremitting in labor or effort; untiring; unwearying; not yielding to fatigue.

Extremely persistent and untiring.