- absolutely trustworthy or sure: an infallible rule.
- unfailing in effectiveness or operation; certain: an infallible remedy.
- not fallible; exempt from liability to error, as persons, their judgment, or pronouncements: an infallible principle.
- 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.
- an infallible person or thing.
- not fallible; not liable to error
- not liable to failure; certain; surean infallible cure
- completely dependable or trustworthy
- a person or thing that is incapable of error or failure