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

Smith has never been the indefatigable champion of free enterprise imagined by his acolytes. —Literary Hub, 9 Mar. 2026

Some of the more seasoned staff, including and especially the indefatigable charge nurse Dana Evans (Katherine LaNasa), remember the days before everyone carried an iPad well enough to keep things moving. —Culture Critic, Los Angeles Times, 6 Mar. 2026

But on his latest album, In My Dreams, recorded between live shows and the studio, the easygoing savant stops to assess his indefatigable career, still equipped with his signature experimentalism and his longstanding penchant for collaboration. —Archie Forde, Pitchfork, 6 Mar. 2026

Anderson remained an indefatigable businesswoman throughout her life, managing the Fairmont Apartments until her death at the age of 87 and, odds are, owning a car outfitted with the wiper successor of her 1903 invention. —Shoshi Parks, Popular Science, 4 Mar. 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