1. (

• foolproof ,
• unfailing

) not liable to failure; "a foolproof identification system"; "the unfailing sign of an amateur"; "an unfailing test" ;

2. (

• unfailing

) always able to supply more; "an unfailing source of good stories"; "a subject of unfailing interest" ;

3. (

• unfailing ,
• unflagging

) unceasing; "unfailing loyalty"; "unfailing good spirits"; "unflagging courtesy" ;