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

That’s a shame, but Garrett remains indefatigable. —Brad Sanders, Pitchfork, 14 Apr. 2026

The indefatigable ability to get back in the blocks, knowing that 99 times out of 100 failure is almost certain. —Courtney Crowder, USA Today, 10 Apr. 2026

How crazy busy is this indefatigable powerhouse? —Madeleine Marr, Miami Herald, 7 Apr. 2026

Kikuyu, however, is the ultimate in dog-tolerant grasses with its indefatigable, ropy stolons and rhizomes. —Joshua Siskin, Oc Register, 4 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