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

• inexhaustible
• tireless
• unflagging
• untiring
• weariless

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

Examples of such indefatigable, innovative individuals abound in these pages. —Naazneen Karmali, Forbes.com, 6 June 2025

Zsa-zsa is a survivor and a fighter and an indefatigable entrepreneur; his relentless energy is matched by nothing else other then Alexandre Desplat’s thrilling ticking time bomb of a score. —Amy Nicholson, Los Angeles Times, 29 May 2025

Schur co-created the series with Greg Daniels, while Poehler starred as indefatigable government employee Leslie Knope. —Joe Otterson, Variety, 7 May 2025

Right up until her late 70s, Mom was indefatigable, still kicking up her heels at weekly polka dances and taking bus trips with her girlfriends to Mohegan Sun casino in Connecticut. —Barbara Ellis, Denver Post, 11 May 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