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  • Adj.




My sister is indefatigable or tireless in her efforts on behalf of the homeless. She volunteers at the shelter everyday and writes to her senator constantly with an indefatigable, endless determination. She never seems to tire of coming up with new ways to help. She is an indefatigable, energetic, and highly active defender of the rights of those who are in need.

Quiz: How does an indefatigable person do something?

  • They show effort—but not enough to complete the task.
  • They seem able to do it without losing any energy.
  • They delegate the responsibility to someone else.

Memory Hook

Big, Fat, and Undependable Don't tell me that a big, fat, and undependable soccer player will be indefatigable! How could he move that much weight around the field without getting exhausted?


  • The indefatigable pursuit of an unattainable perfection—even though nothing more than the pounding of an old piano—is what alone gives a meaning to our life on this unavailing star. — Logan Pearsall Smith, American-born British writer, from _Afterthoughts_ Logan pearsall smith, american-born british writer, from _afterthoughts_
  • The indefatigable Guggenheim, which already operates branches in Berlin and Venice, has plans for a $687 million building at the southern tip of Manhattan and is also casting its eyes on Brazil. —Newsweek
  • Perhaps one of the most striking impressions one takes from _My Life in France_ is of [Julia] Child’s indefatigable attention to detail and insistence on an exact, careful approach to cooking. She would investigate ingredients to learn all she could about them, and test and retest recipes for as long as it took to get them just right. —The Christian Science Monitor
  • Bethe worked into his 90s at Cornell University’s Newman Laboratory of Nuclear Studies, devoting many solitary afternoons to his passion: numbers. . . . Bethe’s indefatigable aura earned him the nickname of "The Battleship" at Los Alamos, the laboratory in New Mexico where the atomic bomb was developed. —Sarasota Herald-Tribune

Word Ingredients

in- not
de- from
fatig weary, tire
-able handy, capable of

An athlete who is indefatigable is “not capable of tiring or wearying from” effort.

Word Constellation