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

• 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

This year, the indefatigable founder and principal designer of his eponymous brand marks 40 years in the business at a time when his reimagined vision for preppy is resonating with both his loyal fans and a new crop of Gen Z consumers. —Katie Abel, Footwear News, 23 Oct. 2025

Their rugged endurance is what endears Jeeps to car-lovers with a sense of history and who appreciate the significance of a vehicle that defined an indefatigable generation. —Robert Ross, Robb Report, 17 Oct. 2025

Indeed, inspired by the indefatigable Rice, who was making last-ditch blocks at one end after chasing half the length of the pitch and setting up goals at the other, there was a resilience and relentlessness about Arsenal against Newcastle that spoke volumes for their mentality. —Stuart James, New York Times, 29 Sep. 2025

Sheeran, an indefatigable road warrior, finished his worldwide Mathematics Tour earlier this year after spanning the globe since 2022. —Melissa Ruggieri, USA Today, 18 Sep. 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