What does indefatigable mean?
Indefatigable describes a person, quality, or activity marked by extraordinary persistence. Someone who is indefatigable does not simply avoid fatigue; they continue working steadily despite difficulty, repetition, and discouragement. The word is often used for people whose efforts sustain them through demanding tasks, such as researchers, teachers, volunteers, or performers. It may also modify qualities such as energy, attention, or optimism, especially when these qualities seem unusually durable. The expression is more common in formal writing, journalism, and commemorative speech than in casual conversation. Because it carries a strongly laudatory tone, it can suggest admirable endurance, but context may make it mildly ironic when applied to needless or excessive persistence. Overall, indefatigable is a precise and memorable word for tireless perseverance that continues in the face of fatigue.
adjectiveIncapable of being worn out by effort; persevering tirelessly despite fatigue.
- Incapable of being exhausted or discouraged by continued effort; persevering tirelessly.
"Her indefatigable determination transformed an ordinary project into an extraordinary achievement."
"The indefatigable volunteers continued working long after everyone else had gone home."
"Despite years of setbacks, she remained indefatigable in her pursuit of a cure."
From Latin for “not tired,” indefatigable is a grand word for the kind of persistence that never runs out of steam.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does indefatigable come from?
Indefatigable comes from Latin indefatigabilis, meaning “not subject to tire” or “not tired.” It was formed from the prefix in-, meaning “not,” and fatigare, meaning “to tire” or “wear out.” The word entered English in the early 17th century and developed through French, while its relatives fatigue, fatigable, and fatiguing belong to the same Latin root.
Related word forms
How indefatigable is actually used
Usually formal or literary. It is strongly approving and suggests exceptional persistence, though it can occasionally be used ironically to describe someone whose relentless efforts seem excessive.