indefatigable

IPA/ˌɪndɪˈfætɪɡəbl/
KK[ˌɪndɪfˈætɪɡəbəl]IPA/ˌɪndɪˈfætɪɡəbl/

indefatigable — adjective

  • indefatigablepositive
  • more indefatigablecomparative
  • most indefatigablesuperlative

1. always full of energy and continuing to work toward a goal without ever showing

1.adjectiveC1
Definition

always full of energy and continuing to work toward a goal without ever showing signs of tiredness or giving up

Example

The indefatigable nurse Chidi worked two extra shifts without complaining.

attributive: indefatigable + noun

Even after hiking for twelve hours, Anjali remained indefatigable and cheerful.

remained + indefatigable (predicative)

Common collocations
  • indefatigable worker
  • indefatigable researcher
  • indefatigable volunteer
  • indefatigable campaigner
  • indefatigable energy
  • indefatigable enthusiasm
  • indefatigable efforts
  • indefatigable in one's pursuit
  • indefatigable in one's work
Synonyms
  • tireless

    most common alternative; slightly less formal and used in a wider range of contexts

  • untiring

    very similar in meaning; also somewhat formal and literary

  • unflagging

    emphasises steady, constant energy that does not diminish over time

  • persevering

    focuses on continuing despite difficulties rather than lack of fatigue

Antonyms
  • lazy

    suggests a lack of willingness to make an effort, rather than becoming tired

  • lethargic

    implies a lack of energy or enthusiasm, often due to illness or low mood

  • weary

    describes a state of tiredness rather than a personality trait

Grammar Patterns

indefatigable + noun

be indefatigable in/at + noun/gerund

Usage Note

Common in formal or literary contexts; rarely used in everyday casual conversation. Often describes a person's approach to work, study, service, or a long-term goal.

Common Mistakes

She became indefatigable after a short rest.
She remained indefatigable even after working all night.
'indefatigable' describes a lasting quality, not a temporary state that comes and goes after rest.
My friend is indefatigable at playing video games.
The researcher was indefatigable in her pursuit of a cure.
'indefatigable' is formal and typically used for serious or sustained efforts, not casual leisure activities.

Word family

Synonym discussion

Sense: adjective/1

All four words describe sustained effort, but they differ in nuance and register. "Tireless" is the most common and neutral term — it simply means not becoming tired (a tireless advocate for children's rights). "Untiring" is very similar in meaning but sounds slightly more formal and literary. "Unflagging" emphasises that one's energy or enthusiasm does not fall or weaken over time (unflagging support for the cause). "Indefatigable" itself is the most formal and emphatic of the group, connoting both an inability to feel fatigue and an unwillingness to stop. "Persevering" takes a slightly different angle: it focuses on continuing despite obstacles or hardship rather than on not getting tired. In everyday writing, "tireless" is the safest choice; "indefatigable" adds a tone of admiration and formality suitable for tributes, biographies, and formal acknowledgements.

tireless ↗untiring ↗unflagging ↗persevering ↗

Common collocations

Nouns

Adverbs

Phrases

  • indefatigable in one's pursuit of
  • indefatigable in one's work

Prepositions

Etymology

LatinFrenchEnglish

Comes from Latin 'indefatigabilis', formed from 'in-' (not) and 'defatigare' (to tire out — itself from 'de-' meaning thoroughly + 'fatigare' meaning to weary). The word entered English through French 'indéfatigable' in the early 1600s, carrying the sense of someone who cannot be worn down by effort.