fail–safe

not likely to fail men have traditionally regarded flowers as the fail-safe gift for Valentine's Day Synonyms can't-miss, certain, fail-safe, sure, surefire, unfailingRelated Words dependable, reliable; deadly, unerringNear Antonyms doubtful, questionable, uncertainAntonyms fallible

a measure taken to preclude loss or injury there are so many fail-safes built into the system that a highly unlikely series of mistakes would have to be made before failure could occur Synonyms caution, fail-safe, palladium, preventive, safeguardRelated Words armor, cover, guard, protection, screen, shield, wall, ward