- not failing; not giving way; not falling short of expectation; completely dependable: an unfailing friend.
- inexhaustible; endless: unfailing resources; unfailing good humor.
- not failing; unflagging
- continuous or unceasing
- sure; certain
adj.late 14c., “never coming to an end, unceasing,” from un- (1) “not” + gerundive of fail (v.). Related: Unfailingly.