Definition of fail-safe in US English:



  • 1Causing a piece of machinery or other mechanism to revert to a safe condition in the event of a breakdown or malfunction.

    ‘a forklift with a fail-safe device’
    • ‘The Tangara trains are equipped with a number of fail-safe devices, including one known as a deadman's brake.’
    • ‘If the potential human and economic costs are high enough, engineers who work with floodwater alleviation systems always design them with some sort of fail-safe mechanism.’
    • ‘The other thing we had noticed when Sally had come in to have the warning light checked out was that the transmission was always stuck in third gear, or fail-safe mode.’
    • ‘Since that time the device has gone through rigorous testing to develop tamper-resistant and fail-safe systems.’
    • ‘Eyewear of the appropriate optical density is worn when using devices not equipped with fail-safe mechanisms.’
    • ‘Systems in a reactor work in fail-safe mode, which means that the failure of a system will lead to a safer mode of operation.’
    • ‘With modern systems that relied more on fail-safe electronic units than on mechanical devices that could break down or malfunction at any time, flying had become a lot safer these days.’
    dependable, safe, tried and tested, well built, well engineered, good
    View synonyms
    1. 1.1 Unlikely or unable to fail.
      ‘the computer that runs the place is supposed to be fail-safe’
      • ‘The major motivation of new collectors seems to be the perception that art is a fail-safe investment, like a government guaranteed tax-free fixed deposit with spectacular interest rates.’
      • ‘I'm violently opposed to taking that on, but somehow I do believe that government will have to have a fail-safe protection on that piece of the retirement expense.’
      • ‘If you're getting mixed signals, give the subject this fail-safe test on a piece of paper.’
      • ‘While sensible, it is not a fail-safe precaution.’
      • ‘There were fail-safe steps in place, and they didn't work.’
      • ‘They also see prompts as a means for new users to teach themselves to use a device in a fail-safe manner.’
      • ‘And there is no fail-safe way to prevent people from gaining access to semi-automatic weapons - without banning them from the public at large.’
      • ‘But should the worse-case scenario happen, Robert teaches women some fail-safe moves which would disable an assailant.’
      • ‘As a result of the impact of failure, aerospace systems have greater redundancy and fail-safe requirements.’
      • ‘It's pretty fail-safe, but you still have to pay attention to what you're doing.’
      • ‘We need more certainty about bias, some dependable, fail-safe test.’
      • ‘For the uninitiated, most ground forces still employ a final fail-safe method for testing the air before giving the ‘all clear’ message to soldiers wearing their gas masks.’
      • ‘The good news is that having your teeth professionally whitened is not only affordable, which should last a lifetime with occasional top-ups - it is also a simple, noninvasive and virtually fail-safe procedure.’
      • ‘Check the software to verify if it has fail-safe and recovery procedures.’
      • ‘She wants not only clearer labelling but also a fail-safe device which would make it impossible for a drug to be wrongly administered.’
      • ‘The campaign also has two back-up credit card transaction systems in place (one built in-house and one by a consultant) for high traffic periods and as a fail-safe procedure.’
      • ‘That is wise, but it seems to me the most fail-safe way to protect a corporate network from viruses is to prevent their entrance into the system in the first place.’
      • ‘It's a cheap one, and does not seem to have some form of fail-safe opening-from-the-outside device, for people that have forgotten their keys.’
      • ‘In the main this system works well, but it is not entirely fail-safe.’
      • ‘Columbia was the first spacecraft to disintegrate on re-entry to the Earth's atmosphere - and the results, in falling debris, were a shocking lesson to the engineers responsible for fail-safe planning.’


  • usually in singular A system or plan that comes into operation in the event of something going wrong or that is there to prevent such an occurrence.

    ‘the secondary safety system is indeed a fail-safe’
    • ‘Scary enough, but the researchers also found that the corrupted system's self-analysing fail-safe would itself sometimes fail to detect the anomaly.’
    • ‘It has never really disappeared from our wardrobes, but the blazer, once a conservative fail-safe, is now the latest in casual chic.’
    • ‘But, as I imagine it was meant to do, it was also reassuring to see what fail-safes and other options exist in even the direst circumstances.’
    • ‘Elements of information on the certificate are placed in a particular way so as to act as a fail-safe against any crude counterfeit efforts.’
    • ‘A small auxiliary throttle is used as a fail-safe should the system fail, to control fuel tank ventilation, and to improve cold starts.’
    • ‘I imagine there were fail-safes against something like that.’
    • ‘Before he ever reached another catatonic state, emergency fail-safes would activate.’
    • ‘A large fund was set up with a set of strict guarantees and fail-safes to provide the stream of income required for the maintenance of my crypt.’
    • ‘I have my master plan set, as well as fail-safes in position as well.’
    • ‘Ramirez sat down, and typed in his personal code, overriding the General's fail-safes and security measures as he retook control of the automated defence systems.’
    • ‘While no one is saying anything for certain - and even though the company has some corruption fail-safes built into its software, the inkling seems to be that it is probably some kind of software glitch.’
    • ‘As an example, if you order a server from the company, when the order is submitted fail-safes within the system will alert us if a mistake has been made and won't allow the server to be configured incorrectly.’
    • ‘In addition, all federally funded prevention materials would be required to include information warning people that condoms are not 100 percent fail-safe.’
    • ‘Many shooters don't understand the purpose of such a dual action, assuming that the pump mechanism is a fail-safe against a malfunction with the semiauto mode.’
    • ‘We obviously have a great understanding of the system and there are numerous fail-safes, but it does get sporty.’
    • ‘There's gonna be a lot of fail-safes put in place between state, local and federal law enforcement agencies.’
    • ‘Right now, he sees you as some kind of fail-safe that he can rely on.’
    • ‘The big important systems such as atmosphere, food, environmental, navigation, and drill were protected with so many back-ups and fail-safes that it was almost impossible for them to freeze.’
    • ‘The fail-safes on the program alert us when something gets neglected.’
    • ‘There are just so many fail-safes that you have to build in, because you only get one chance, and the cameras of the world are on you.’



/ˈfāl ˈˌsāf//ˈfeɪl ˈˌseɪf/