indefatigable
in·de·fa·tigable
adjective
1.
showing sustained enthusiastic action with unflagging vitality
- “an indefatigable advocate of equal rights”
- “a tireless worker”
- “unflagging pursuit of excellence”
Origin
From Middle French, from Latin indēfatīgābilis (“untiring”), from in- (“not”) + dēfatīgō (“to tire out”).
Related words
Word family
WordNet 2.1 (Princeton University). Wiktionary (CC BY-SA). CMU Pronouncing Dictionary. WordNet 2.1 Copyright Princeton University. All rights reserved. Wiktionary content is available under the Creative Commons Attribution-ShareAlike Licence.