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indefatigable

adjective
 
 
/ˌɪn.dɪˈfæt.ɪ.ɡə.bl̩/ US  /-ˈfæt̬-/ formal

Definition

always determined and energetic in trying to achieve something and never willing to admit defeat: Annie was an indefatigable campaigner for better community services.Energetic and lively indefatigably
 
 
/-bli/ adverb
Energetic and lively
(Definition of indefatigable adjective from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)

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