infallible

adjective3

1. •
   Without fault or weakness; incapable of error or fallacy.

   • He knows about many things, but even he is not infallible.
2. •
   Certain to produce the intended effect; sure.

   • Try this infallible cure for hiccups.
3. •
   Certain to result from a specific cause; inevitable.

noun1

1. •
   A person who, or an object or process that, is taken as being infallible.

noun1

1. •
   Any of the fourteen central religious figures believed by Twelver Shia Muslims to be infallible, consisting of Muhammad, his daughter Fatima, and the Twelve Imams recognized by Twelvers.