/ ɪnˈfæləbl; NAmE / adjective
1.
never wrong; never making mistakes :
infallible advice
Doctors are not infallible.
OPP fallible
2.
that never fails; always doing what it is supposed to do :
an infallible method of memorizing things
► in·fal·li·bil·ity / ɪnˌfæləˈbɪləti; NAmE / noun [ U ]:
papal infallibility
► in·fal·libly / -əbli; NAmE / adverb
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WORD ORIGIN
late 15th cent.: from French infaillible or late Latin infallibilis , from in- not + Latin fallere deceive.