Simple Definition of indefatigable

from our Learner's Dictionary

indefatigable

adjective

ˌɪndɪˈfætɪgəbəl

formal : able to work or continue for a very long time without becoming tired : tireless

an indefatigable campaigner

a person of indefatigable patience/enthusiasm/optimism

Cite this Entry

Style

“Indefatigable.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/indefatigable. Accessed 18 Apr. 2026.

Copy Citation

Popular in Grammar & Usage

Are You Misusing These 10 Common Words?

5 Verbal Slip Ups and Language Mistakes

Is it 'nerve-racking' or 'nerve-wracking'?

'Sneaked' or 'Snuck': Which is correct?

The Difference Between 'i.e.' and 'e.g.'

Popular in Wordplay

Simple Definition of indefatigable

indefatigable

adjective

Cite this Entry

More from Merriam-Webster on indefatigable

More from Merriam-Webster

Word of the Day

hiatus

Popular in Grammar & Usage

Are You Misusing These 10 Common Words?

5 Verbal Slip Ups and Language Mistakes

Is it 'nerve-racking' or 'nerve-wracking'?

'Sneaked' or 'Snuck': Which is correct?

The Difference Between 'i.e.' and 'e.g.'

Popular in Wordplay

The Longest Long Words List

The Opposite of Déjà Vu

The Words of the Week - Apr. 17

Was 'nervous Nellie' a Real Person?

Even More Bird Names that Sound Like Insults (and Sometimes Are)

Popular

Are You Misusing These 10 Common Words?

The Longest Long Words List

The Opposite of Déjà Vu

Games & Quizzes