indefatigable

[in-di-fat-i-guh-buhl] / ˌɪn dɪˈfæt ɪ gə bəl /

ADJECTIVE

untiring

Synonyms

STRONGEST

assiduous diligent dogged energetic inexhaustible painstaking relentless tireless unflagging unwavering vigorous

WEAK

active bound and determined dead set on determined hell-bent industrious ironclad nose to grindstone patient persevering persistent pertinacious sedulous steadfast stop-at-nothing strenuous unfaltering unflinching unremitting unwearied unwearying

Antonyms

STRONGEST

changing idle inactive indifferent lazy lethargic negligent tired wavering

WEAK

fatigued weary

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

But an indefatigable Volkanovski's agility and relentless striking eventually wore down his flagging challenger, who was unable to land a knockout in the final round.

From Barron's • Feb. 1, 2026

Mr. Dooley is also a discerning and indefatigable researcher.

From The Wall Street Journal • Jan. 21, 2026

It also said he was "indefatigable to the end" and "driven by relentless curiosity and a deep attention to the present and to people".

From BBC • Sep. 4, 2025

They deserve our support, as do a slew of writers, such as the indefatigable Heather Cox Richardson and Ruth Ben-Ghiat, who publish via Substack.

From Salon • Jul. 5, 2025

With his mind’s eye, Bernard saw' the needle on the scent meter creeping round and round, antlike, indefatigable.

From "Brave New World" by Aldous Huxley

Vocabulary lists containing indefatigable

Animal Farm

Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!

The Scarlet Letter

Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!

The Haunting of Hill House

Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!