fail-safe

[feyl-seyf]

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

1. (sometimes initial capital letter),  the point beyond which the bombers cannot go without specific instruction; the fail-safe point.

2. 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 

1. to make fail-safe.

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

1. (intr) to return to a safe condition in the event of a failure or malfunction

Word History and Origins

Origin of fail-safe¹

First recorded in 1945–50; apparently from verb phrase to fail safe(ly)

Example Sentences

“Within moments, the robot came to a full stop in response to sensing a pedestrian in close proximity, which is considered its fail-safe state.”

Read more on Los Angeles Times

There’s no 100% safe way to lift 500 pounds, just like there is no fail-safe way of throwing 100 mph.

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One significant solution implemented as a fail-safe for Level 4 automated vehicles is the concept of remote driving.

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And because airplanes are packed with fail-safes, there are times when a flight with a malfunctioning system can safely proceed simply by relying on one or more backups instead.

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This is a fail-safe scenario but the converse "wrong side" failures -- when the signal goes from red to green -- are much more hazardous.

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