indefatigable

From Middle French, from Latin indēfatīgābilis (“untiring”), from in- (“not”) + dēfatīgō (“to tire out”).

• (Received Pronunciation) IPA^(key): /ˌɪn.dɪˈfæ.tɪ.ɡə.bəl/
• (General American) IPA^(key): /ˌɪn.dəˈfæ.tɪ.ɡə.bəl/, [ˌɪn.dəˈfæ.ɾɪ.ɡə.bəl]

• Audio (AU)

  (file)

• (sometimes proscribed) IPA^(key): /ˌɪn.dɪ.fəˈti.ɡə.bəl/, /ˌɪn.də-/

• Audio (Northern California, US)

  (file)

• Hyphenation: in‧de‧fa‧tig‧a‧ble

indefatigable (comparative more indefatigable, superlative most indefatigable)

1. Extremely persistent and untiring.

   Synonyms: inexhaustible, relentless, tireless, unflagging, unsinkable, untiring, unwearying

   Antonym: (much less common) defatigable

   • 1704, [Jonathan Swift], “Section I. The Introduction.”, in A Tale of a Tub. […], London: […] John Nutt, […], OCLC 752990886, page 33:

     Whoever hath an Ambition to be heard in a Crowd, muſt preſs, and ſqueeze, and thruſt, and climb with indefatigable Pains, till he has exalted himſelf to a certain Degree of Altitude above them.

   • 1749, Henry Fielding, “Containing Two Letters in Very Different Stiles”, in The History of Tom Jones, a Foundling, volume VI, London: A[ndrew] Millar, […], OCLC 928184292, book XVIII, page 196:

     [...] But he was at the ſame Time an excellent Scholar, and moſt indefatigable in teaching the two Lads.

   • 1895–1897, H[erbert] G[eorge] Wells, “Friday Night”, in The War of the Worlds, London: William Heinemann, published 1898, OCLC 699873, book I (The Coming of the Martians), pages 54–55:

     All night long the Martians were hammering and stirring, sleepless, indefatigable, at work upon the machines they were making ready, and ever and again a puff of greenish-white smoke whirled up to the starlit sky.

   • 2020, Jeph Jacques, Questionable Content (webcomic), 4302: Bowed But Unbroken:

     "Oh, Roko! You're so indefatigable! Nothing gets you down!"