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

The once irrepressible and indefatigable Turner was slowed late in life by a progressive brain disorder. —Christopher Quinn, AJC.com, 6 May 2026

Declan Rice was indefatigable, inspired to make a difference all over the pitch. —Amy Lawrence, New York Times, 6 May 2026

And while Marisa Abela has the indefatigable Industry boosters behind her, we’ve been burned by Emmy hope for that show before. —Joe Reid, Vulture, 2 May 2026

Donte DiVincenzo is an indefatigable source of hustle and aggression who has flipped numerous games this season with strings of energy plays. —Jace Frederick, Twin Cities, 29 Apr. 2026

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