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

Synonyms for indefatigable Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for indefatigability

Historical Examples of indefatigability

British Dictionary definitions for indefatigability



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 indefatigability

1630s, from indefatigable + -ity.



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