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


incapable of being tired out; not yielding to fatigue; untiring.

Origin of indefatigable

1580–90; < Latin indēfatīgābilis untiring, equivalent to in- in-3 + dēfatīgā(re) to tire out (see de-, fatigue) + -bilis -ble
Related formsin·de·fat·i·ga·bil·i·ty, in·de·fat·i·ga·ble·ness, nounin·de·fat·i·ga·bly, adverb Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for indefatigable

British Dictionary definitions for indefatigable


/ (ˌɪndɪˈfætɪɡəbəl) /


unable to be tired out; unflagging
Derived Formsindefatigability or indefatigableness, nounindefatigably, adverb

Word Origin for indefatigable

C16: from Latin indēfatīgābilis, from in- 1 + dēfatīgāre, from fatīgāre to tire
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for indefatigable



1580s (implied in indefatigably), from French indefatigable (15c.), from Latin indefatigabilis "that cannot be wearied," from in- "not" (see in- (1)) + defatigare "to tire out," from de- "utterly, down, away" + fatigare "to weary" (see fatigue).

Online Etymology Dictionary, © 2010 Douglas Harper