fail-safe
Americanadjective
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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.
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equipped with a secondary system that insures continued operation even if the primary system fails.
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(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.
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guaranteed to work; totally reliable.
a fail-safe recipe for a cheese soufflé.
noun
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(sometimes initial capital letter) the point beyond which the bombers cannot go without specific instruction; the fail-safe point.
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something designed to work or function automatically to prevent breakdown of a mechanism, system, or the like.
verb (used with object)
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fail-safes,
present (3rd person singular)
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fail-safed,
past participle, past
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fail-safing
present participle
adjective
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designed to return to a safe condition in the event of a failure or malfunction
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(of a nuclear weapon) capable of being deactivated in the event of a failure or accident
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unlikely to fail; foolproof
verb
Other Word Forms
Inflected Forms
Participles
Conjugated Forms
Present
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fail-safesimple
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fail-safessimple
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have fail-safedperfect
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has fail-safedperfect
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am fail-safingprogressive
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are fail-safingprogressive
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is fail-safingprogressive
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have been fail-safingperfect progressive
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has been fail-safingperfect progressive
Past
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fail-safedsimple
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had fail-safedperfect
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was fail-safingprogressive
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were fail-safingprogressive
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had been fail-safingperfect progressive
Future
Etymology
Origin of fail-safe
First recorded in 1945–50; apparently from verb phrase to fail safe(ly)
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
See Examples For:
Another issue identified by the investigation was that no fail-safe system - involving valve position indicators and gas pressure sensors - had been installed to alert the crew that the valve was failing.
From BBC ● Sep. 8, 2026
Even if you plan to be fully engaged with managing money into retirement, a financial adviser could be a fail-safe if you can no longer make sound decisions.
From The Wall Street Journal ● Nov. 5, 2025
“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.”
From Los Angeles Times ● Sep. 25, 2025
One significant solution implemented as a fail-safe for Level 4 automated vehicles is the concept of remote driving.
From Science Daily ● Nov. 21, 2024
Upon arrival in the town or reservation, Irwin would trot the horses off the railcars and straight to the nearest back road or bullring, where he would implement a nearly fail-safe betting system.
From "Seabiscuit: An American Legend" by Laura Hillenbrand
However, discussions of fall-backs and fail-safes have not been welcome in the Wales camp while the possibility of automatic qualification remains.
From BBC ● Nov. 20, 2023
The second thing that people need to be thinking about here is, what other fail-safes do you have built in place?
From Scientific American ● Dec. 15, 2021
It needs fail-safes that make it easier for factories to restart after being shut.
From Seattle Times ● Oct. 17, 2021
The local election board reported a simpler story: A new worker had incorrectly trashed the ballots, and its fail-safes had quickly identified the problem.
From New York Times ● Sep. 30, 2020
An inmate had escaped from the Rikers Island Visit Room that same summer, despite the many fail-safes.
From "Newjack: Guarding Sing Sing" by Ted Conover
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
