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)
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:
The boats had rejected their inputs and automatically idled as a fail-safe, making them “dead” in the water.
From The Wall Street Journal ● Nov. 27, 2025
He said the boats went “dead in the water” as an automatic fail-safe, which prevented them from causing damage or injury.
From The Wall Street Journal ● Nov. 27, 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
The penalty for entering a fail-safe command “with insufficient reason” was prison, fines, but Margery thought the legal system didn’t go far enough.
From Slate ● Jan. 27, 2024
Whenever those thoughts spring up, my sister is the fail-safe.
From "Challenger Deep" by Neal Shusterman
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.
From New York Times ● Jun. 19, 2024
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
“There are all sorts of fail-safes built into the system to avoid falsely accusing somebody of something,” Scollay said as the sport began the wait for the second result and Medina Spirit headed for Pimlico.
From Washington Post ● May 10, 2021
“Only the person who activated the STM can use it again. My mom has fail-safes against everything.”
From "The First State of Being" by Erin Entrada Kelly
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.
