fail-safe >> ˈfeɪlseɪf
Definition: [adjective] causing a piece of machinery to revert to a safe condition in the event of a breakdown or malfunction.
Example: a forklift truck with a fail-safe device
Definition: [adjective] unlikely or unable to fail.
Example: there is no guaranteed fail-safe procedure
Definition: [noun] a system or plan that comes into operation in the event of something going wrong or that is in place to prevent such an occurrence.
Example: stewards positioned around the track as a fail-safe