fail-safe
1. [ adjective ] guaranteed not to fail
Examples:

"a fail-safe recipe for cheese souffle"

Related terms: secure
2. [ adjective ] eliminating danger by compensating automatically for a failure or malfunction
Examples:

"a fail-safe device in a nuclear weapon to deactivate it automatically in the event of accident"

Related terms: safe
Similar spelling:   falsifier
  falsify
  falsifiable
  falsifying
  false_face
  false_fruit