Having or showing a capacity for persistent effort; not tiring or relenting: a tireless advocate; tireless efforts.
Synonyms: tireless, indefatigable, unflagging, untiring, unwearied, weariless
These adjectives mean having or showing a capacity for persistent or prolonged effort: a tireless worker; an indefatigable advocate of human rights; unflagging pursuit of excellence; untiring energy; an unwearied researcher; a weariless defender of freedom of the press.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.