indefatigable

[in-di-fat-i-guh-buhl]

adjective

1. incapable of being tired out; not yielding to fatigue; untiring.

   Synonyms: persevering, inexhaustible, tireless

indefatigable

/ ˌɪndɪˈfætɪɡəbəl /

adjective

1. unable to be tired out; unflagging

Other Word Forms

• indefatigability noun
• indefatigableness noun
• indefatigably adverb

Word History and Origins

Origin of indefatigable¹

1580–90; < Latin indēfatīgābilis untiring, equivalent to in- in- ³ + dēfatīgā ( re ) to tire out ( de-, fatigue ) + -bilis -ble

Word History and Origins

Origin of indefatigable¹

C16: from Latin indēfatīgābilis, from _in- ¹ + dēfatīgāre, from fatīgāre to tire

Example Sentences

It’s a rollicking animal story; it’s also a tale of indefatigable love.

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Underlings have long marveled at his indefatigable work ethic.

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Xenarios, who died of cancer on Sept. 6 at home in New York at age 79, was the indefatigable soul of the organization, leading it for 40 years until her retirement in 2017.

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But she is also indefatigable: She believes that she must win to save democracy, yet she seems to shoulder that formidable burden without breaking a sweat.

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Tony Doherty, chair of the Bloody Sunday Trust, said: "This day is a tribute to the strength of the families, whose indefatigable campaign for justice has made this happen."

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Related Words

• assiduous 
• diligent 
• dogged 
• energetic 
• inexhaustible 
• painstaking 
• relentless 
• tireless 
• unflagging 
• unwavering 
• vigorous