Indefatigable

Part of speech: adjective

Pronunciation: /ˌɪn.dɪˈfæt.ɪ.ɡə.bəl/

Definitions

1. Showing tireless energy and persistence, never becoming weary or giving up despite prolonged effort or difficulty
2. Never growing weary or losing determination regardless of how long or demanding a task becomes
3. Characterized by relentless stamina and unwavering commitment that refuses to diminish through sustained exertion

Etymology: Before it described a tireless spirit, "indefatigable" was built from a Latin verb meaning "to tire out" and a negating prefix. The Latin "dēfatīgāre" combined "dē-" (intensifying, "thoroughly") with "fatīgāre" ("to weary"), and the adjective "indēfatīgābilis," "untiring," added "in-" ("not") to make it unwearying. The word passed into Middle French, and English borrowed it from there. The roots lead back to an ordinary physical idea: exhaustion. The Latin "fatīgāre" is also the ancestor of "fatigue," which entered English through French and retains the sense of simple weariness. "Indefatigable" is the negated form of that same tiredness, so the word is literally "not worn out."

Synonyms: unflagging, tireless, untiring, unwearied

Antonyms: fatigued, weary