indefatigable

adjective

in·​de·​fat·​i·​ga·​ble ˌin-di-ˈfa-ti-gə-bəl 

: incapable of being fatigued : untiring

an indefatigable worker

indefatigability

ˌin-di-ˌfa-ti-gə-ˈbi-lə-tē 

noun

indefatigableness

ˌin-di-ˈfa-ti-gə-bəl-nəs 

noun

indefatigably

ˌin-di-ˈfa-ti-gə-blē 

adverb

Synonyms of indefatigable

• meticulous
• tireless
• relentless
• untiring
• unflagging
• conscientious
• inexhaustible
• vigorous
• active
• energetic
• diligent
• intense

Examples of indefatigable in a Sentence

a person of indefatigable patience

an indefatigable laborer who can work from sunrise to sunset

Recent Examples on the Web

Violet, indefatigable through the most desperate early months, had started showing signs of exhaustion in June, when she was charged with simultaneously starting a long-COVID recovery unit and a COVID hospice service. —Andrew Martin, New Yorker, 14 Dec. 2025

Social-media-influencer culture also latched on to the phrase for its own attentional ends, as did brands, the indefatigable scavengers. —Ian Bogost, The Atlantic, 12 Dec. 2025

But as long as as the indefatigable Warren continues to cast her aural spells, the music industry will have a devoted caretaker. —Melissa Ruggieri, USA Today, 10 Dec. 2025

That indefatigable cheerfulness, even when describing scenes that sound brutal to almost anyone else, ran through the entire interview. —Eva Roytburg, Fortune, 5 Dec. 2025

Word History

Etymology

Middle French, from Latin indefatigabilis, from in- + defatigare to fatigue, from de- + fatigare to fatigue

First Known Use

1608, in the meaning defined above

Kids Definition

indefatigable

adjective

in·​de·​fat·​i·​ga·​ble ˌin-di-ˈfat-i-gə-bəl 

: capable of working a long time without tiring : tireless

an indefatigable teacher

indefatigably

-blē 

adverb