fail-safe

noun

1. a mechanism capable of returning to a safe state in case there is a failure or malfunction

adj

1. eliminating danger by compensating automatically for a failure or malfunction

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

2. guaranteed not to fail

e.g. a fail-safe recipe for cheese souffle

1. 有自动保险装置的;具有自动防故障性能的
Something that is fail-safe is designed or made in such a way that nothing dangerous can happen if a part of it goes wrong.

e.g. The camera has a built-in failsafe device which prevents it from working if the right signals aren't received.
照相机有内置自动防故障装置，该装置确保相机在未接到正确信号时不会启动。