indefatigable

 
Pronunciation: /ˌɪndɪˈfatɪgəb(ə)l/

adjective

  • (of a person or their efforts) persisting tirelessly: an indefatigable defender of human rights

Derivatives

indefatigability

Pronunciation: /-ˈbɪlɪti/
noun

indefatigably

adverb

Origin:

early 17th century: from French, or from Latin indefatigabilis, from in- 'not' + de- 'away, completely' + fatigare 'wear out'