Failsafe

[feyl-seyf] /ˈfeɪlˌseɪf/

adjective
1.
Electronics. pertaining to or noting a mechanism built into a system, as in an early warning system or a nuclear reactor, for insuring safety should the system fail to operate properly.
2.
equipped with a secondary system that insures continued operation even if the primary system fails.
3.
(sometimes initial capital letter) of, relating to, or designating a system of coded military controls in which bombers dispatched to a prearranged point as part of a standard operating procedure cannot advance farther without direct orders from a designated authority and cannot have the nuclear warheads they carry armed until they have passed their prearranged point.
4.
guaranteed to work; totally reliable:
a fail-safe recipe for a cheese soufflé.
noun
5.
(sometimes initial capital letter) the point beyond which the bombers cannot go without specific instruction; the fail-safe point.
6.
something designed to work or function automatically to prevent breakdown of a mechanism, system, or the like.
verb (used with object), fail-safed, fail-safing.
7.
to make fail-safe.
adjective
1.
designed to return to a safe condition in the event of a failure or malfunction
2.
(of a nuclear weapon) capable of being deactivated in the event of a failure or accident
3.
unlikely to fail; foolproof
verb
4.
(intransitive) to return to a safe condition in the event of a failure or malfunction
adj.

also fail-safe, fail safe “safe against failure,” 1948, from fail (v.) + safe (adj.). Earliest reference is to furnace burners.