形容词
1. unceasing
e.g. unfailing loyalty
unfailing good spirits
unflagging courtesy
Synonym: unflagging
2. always able to supply more
e.g. an unfailing source of good stories
a subject of unfailing interest
3. not liable to failure
e.g. a foolproof identification system
the unfailing sign of an amateur
an unfailing test
Synonym: foolproof