fail-safe
1 of 2adjective
ˈfāl-ˌsāf 
1
: incorporating some feature for automatically counteracting the effect of an anticipated possible source of failure
2
: being or relating to a safeguard that prevents continuing on a bombing mission according to a preconceived plan
3
: having no chance of failure : infallibly problem-free
the little black dress … has consistently been the fail-safe solution for night 
Vogue
Voguefail-safe
2 of 2noun
: a device or measure that makes something fail-safe
Synonyms
Adjective
- can't-miss
- certain
- infallible
- sure
- surefire
- unfailing
Noun
- caution
- palladium
- precaution
- preventive
- safeguard
See all Synonyms & Antonyms 
Word History
First Known Use
Adjective
1931, in the meaning defined at sense 1
Noun
1975, in the meaning defined above
fail-safe 1 of 2
adjective
as in reliable
not likely to fail flowers have been traditionally regarded as the fail-safe gift for Valentine's Day Synonyms & Similar Words
Relevance
- reliable
- surefire
- infallible
- dependable
- unfailing
- can't-miss
- sure
- deadly
- certain
- unerring
Antonyms & Near Antonyms
- questionable
- doubtful
- fallible
- uncertain
fail-safe
2 of 2noun
as in precaution
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 & Similar Words
- precaution
- preventive
- safeguard
- protection
- caution
- shield
- palladium
- wall
- screen
- armor
- ward
- guard
- cover