- Incapable of being fatigued; not readily exhausted;
unremitting in labor or effort; untiring; unwearying; not yielding to
fatigue; as, indefatigable exertions, perseverance, application.
Meaning of 'indefatigable' (Princeton's WordNet)
1 . indefatigable
[ s]
Meaning (1): - showing sustained enthusiastic action with unflagging vitality