American English

Definition of indefatigable adjective from the Oxford Advanced American Dictionary

 

indefatigable

 adjective
adjective
NAmE//ˌɪndɪˈfæt̮ɪɡəbl//
 
(formal) (approving)
 
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never giving up or getting tired of doing something an indefatigable defender of human rights She was indefatigable in her search for the truth.
indefatigably
 
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NAmE//ˌɪndɪˈfæt̮ɪɡəbli//
 
adverb
See the Oxford Advanced Learner's Dictionary entry: indefatigable