from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Incapable or seemingly incapable of being fatigued; tireless. See Synonyms at tireless.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. Extremely persistent and untiring.

from the GNU version of the Collaborative International Dictionary of English

  • adj. Incapable of being fatigued; not readily exhausted; unremitting in labor or effort; untiring; unwearying; not yielding to fatigue.

from The Century Dictionary and Cyclopedia

  • Not defatigable; incapable of being fatigued; not easily exhausted; not yielding to fatigue; unremitting in labor or effort.
  • Synonyms Unwearied, untiring, tireless, unflagging, persevering, assiduous, persistent, sedulous.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adj. showing sustained enthusiastic action with unflagging vitality


from The American Heritage® Dictionary of the English Language, 4th Edition

Obsolete French indéfatigable, from Latin indēfatīgābilis : in-, not; see in-1 + dēfatīgāre, to tire out (dē-, intensive pref.; see de- + fatīgāre, to weary).

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin indēfatīgābilis ("untiring"), from in- ("not") + de- ("away") + fatīgō ("I tire").


  • Armstrong had long been known as an indefatigable spear-carrier for Harry Chandler, but at this moment he seemed unaware that the wind had shifted at Times headquarters.


  • I thought that, according to George Galloway, only certain Middle Eastern dictators could be termed indefatigable?

    Atlantic Review

  • Larsen: If you're ADD and you still have a kind of indefatigable creative drive ...

    Interview with Stephen Larsen, author, THE FUNDAMENTALIST MIND

  • Could he ever overshadow the 'indefatigable' moment with Saddam Hussein?

    Keep On Rockin' In The Trots World

  • Officers generally understand by the words "indefatigable," and

    The Authoritative Life of General William Booth

  • In his first words to the press on Tuesday from the Florencia airport in Colombia, Moncayo thanked the "indefatigable" Senator Cordoba, Colombians for Peace, the Catholic Church, and the International Red Cross.

    New on

  • WASHINGTON, Aug 26 (OneWorld. net) - Eighty-nine years after U.S. women finally won the right to vote, advocacy groups are pressing the Obama administration to promote women's equality worldwide and paying tribute to an "indefatigable" champion of women's rights, Senator Edward M. Kennedy. (U.S.) - beyond your own borders

  • It hath a kind of indefatigable firmness in it, it hath an unwearied strength to move in the yoke all the day long.

    The Works of the Rev. Hugh Binning

  • His attitude reflects what he says is the "indefatigable" approach that Australian performers in general apply to their careers.


  • Byron testifies (September 14, 1817) that his researches were "indefatigable," that he had "more real knowledge of

    The Works of Lord Byron. Vol. 2


Log in or sign up to get involved in the conversation. It's quick and easy.

  • I had this word yesterday on my Word Of The Day app on my Nook Color.

    June 9, 2012

  • But Mr. Lauren, the indefatigable fashion icon, re-upped through March 2013

    January 6, 2011

  • His life was one of indefatigable labor.

    August 31, 2010

  • I first heard this word in the book "Brave New World". I swear it was used like, every ten pages.

    February 21, 2009

  • I do the inverting the g and t thing, too. It is rather comical, but sometimes very embarrassing.

    January 18, 2008

  • When I'm three sheets to the wind, I tend to invert the g and t, with hilarious results.

    October 23, 2007