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

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

My journey started with an indefatigable New York City lawyer on a quest to give her dying husband a chance. —David Armstrong, CNN Money, 10 May 2025

This stadium show unlocks a new level of accomplishment for the apparently indefatigable Summit, who’s previously played solo headlining sets at large-scale venues including New York’s Madison Square Garden and Los Angeles’ BMO Stadium and Kia Forum. —Katie Bain, Billboard, 8 May 2025

Peters continued to tour and release music during a three-decade battle with several forms of cancer, putting himself up as an indefatigable advocate for blood cancer patients. —Gil Kaufman, Billboard, 29 Apr. 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