Meaning : Not liable to failure.
Example :
A foolproof identification system.
The unfailing sign of an amateur.
An unfailing test.
Synonyms : foolproof
Meaning : Always able to supply more.
Example :
An unfailing source of good stories.
A subject of unfailing interest.
Meaning : Unceasing.
Example :
Unfailing loyalty.
Unfailing good spirits.
Unflagging courtesy.
Synonyms : unflagging