infallible

/ɪnˈfa.lɪ.b(ə)l/

adjective

Without fault or weakness; incapable of error or fallacy.
"He knows about many things, but even he is not infallible."
Certain to produce the intended effect, sure.
"Try this infallible cure for hiccups."

Practice "infallible" in context

WordNote uses spaced repetition across multiple quiz levels, from recognizing the meaning to recalling it in active practice.

No credit card. No install required.