infallible

[in-fal-uh-buhl]

adjective

1. absolutely trustworthy or sure.

   an infallible rule.

2. unfailing in effectiveness or operation; certain.

   an infallible remedy.

3. not fallible; exempt from liability to error, as persons, their judgment, or pronouncements.

   an infallible principle.

4. Roman Catholic Church.,  immune from fallacy or liability to error in expounding matters of faith or morals by virtue of the promise made by Christ to the Church.

noun

1. an infallible person or thing.

infallible

/ ɪnˈfæləbəl /

adjective

1. not fallible; not liable to error

2. not liable to failure; certain; sure

   an infallible cure

3. completely dependable or trustworthy

noun

1. a person or thing that is incapable of error or failure

Other Word Forms

• infallibility noun
• infallibleness noun
• infallibly adverb
• noninfallible adjective
• noninfallibly adverb

Word History and Origins

Origin of infallible¹

First recorded in 1375–1425; late Middle English word from Medieval Latin word infallibilis. See in- ³, fallible

Synonym Study

See reliable.

Example Sentences

But it is a reminder that just like AI, traditional rules of thumb for investing aren’t infallible.

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“Welcome to Swanburne, Incorrigible children! I am Miss Mortimer, and you have just met my little lap cat, Shantaloo. She is infallibly shrewd. See how she already thinks of you as friends?”

Read more on Literature

When the high was good, he felt invincible, infallible, he said, even if he was just sitting on his couch.

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Cult of the infallible leader: While the leader is of course indispensable, his supremacy and dominance would be impossible to maintain without the sycophancy and unquestioning obedience of millions of members of the national community.

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“It has to be thought of as infallible.”

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Related Words

• authoritative 
• flawless 
• foolproof 
• unbeatable