indefatigable

1 of 2

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

indefatigability

2 of 2

noun

in·​de·​fat·​i·​ga·​bil·​i·​ty ¦ində̇ˌfat|ə̇gə¦bilətē 

-dēˌ-, 

-at|, 

|ēg-, 

-ətē, 

-i

plural -es

: the quality or state of being indefatigable

Synonyms of indefatigable

Adjective

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

Examples of indefatigable in a Sentence

Adjective

a person of indefatigable patience

an indefatigable laborer who can work from sunrise to sunset

Recent Examples on the Web

Adjective

And while Foy is appealing as the indefatigable mother, Garfield leans too heavily into manic cutesiness as the endlessly chirpy father who at times seems less grown-up than his children. — Frank Scheck, HollywoodReporter, 20 Aug. 2026

The vehicle’s pearlescent sheen alone is worthy of a moment in the sun, and gives the car a timelessness on par with that of its indefatigable owner. — Viju Mathew, Robb Report, 15 Aug. 2026

After Graham was eulogized Tuesday in the nation's capital as an indefatigable dealmaker by the president, vice president and others, mourners in Columbia prepared to remember him Wednesday as the son of pool hall owners who never forgot his roots. — ABC News, 29 July 2026

In June 2022, the indefatigable band embarked on a 60th anniversary tour, which began in Madrid and wrapped in August in Berlin. — Stephanie Sengwe, PEOPLE, 27 July 2026

Word History

Etymology

Adjective

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

First Known Use

Adjective

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