I'm looking for a word (or phrase) to describe mechanisms that are perfectly functional even when they aren't functioning as expected.

Examples of these include:

  • Escalators & Electric Walkways: Even when they aren't powered these systems still function as perfectly adequate stairs or sidewalks
  • Mopeds: Even when out of gas, the owner can still pedal along
  • Electric Toothbrushes: One can still brush their teeth without turning it on

I've considered using engineering and management terms such as redundant mechanisms, enhanced systems, or fault-tolerant machines that come close, but those terms refer to very specific technical concepts that don't apply to my needs or the the examples.

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    This is an excellent question, to which I don’t have an answer. I imagine this sort of thing must be quite difficult to Google, but I’m sure you’ve tried looking around for a word to describe the concept before asking here. In order to show your own research efforts (and prevent potential close votes), you should edit the question and add in a description of what you’ve tried and why that led to no satisfactory result. Commented Oct 3, 2019 at 14:01
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    From wikipedia : A fault-tolerant design enables a system to continue its intended operation, possibly at a reduced level, rather than failing completely, when some part of the system fails Is that not okay in both a technical and everyday-speech context ?
    – k1eran
    Commented Oct 3, 2019 at 14:53
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    If there's no power and you're out of gas, all those devices will have to operate in legacy mode. Luckily, all of them are backwards compatible; a sonic tongue cleaner, not so much. - "behaves in a way different from its standard operation in order to support older software, data, or expected behavior."
    – Mazura
    Commented Oct 4, 2019 at 1:51
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    @nick012000 - My point is you're talking about a type of serious malfunction that (YouTube videos notwithstanding) is relatively rare. More commonly when an escalator fails it is much less serious and shuts down and the owners often turn it off and leave it accessible as stationary stairs until it can be repaired. I believe that is what the OP asked about.
    – nnnnnn
    Commented Oct 4, 2019 at 5:49
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    Even a stopped clock gives the right time twice a day.
    – Sentinel
    Commented Oct 4, 2019 at 22:41

13 Answers 13


If it avoids catastrophic failure, it exhibits:

graceful degradation - Graceful degradation is the ability of a computer, machine, electronic system or network to maintain limited functionality even when a large portion of it has been destroyed or rendered inoperative. The purpose of graceful degradation is to prevent catastrophic failure. Ideally, even the simultaneous loss of multiple components does not cause downtime

I do not think you will find one word for these things. They are not "working" as designed... they have failed. They simply have failed in a way that doesn't completely destroy their utility, but that's not to say they couldn't fail that way. The wheels could fall off the moped, the brush on the electric toothbrush could break off.

You're more describing a failure mode than a specific variety of things. So, another answer geared at a description, rather than one word.

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    I think he's looking for something that is understandable without jargon, not so much a single word. I like this answer, though.
    – David M
    Commented Oct 3, 2019 at 16:28
  • Graceful degradation is more for things like each node on the net continuing to function even when other nodes are failing or misbehaving. It does not mean that you can still use your PC as a limited computer if the power is off.
    – puppetsock
    Commented Oct 3, 2019 at 16:51
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    Its used in an aviation context here aviation.stackexchange.com/questions/43919/… ... meaning you can fly the plane even when some electronic components fail
    – stevesliva
    Commented Oct 3, 2019 at 16:54
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    In this case I'd prefer graceful failure. Degradation implies a steady decline in performance, while the examples imply more of a sudden fault.
    – Chris H
    Commented Oct 4, 2019 at 13:20
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    @EdwinAshworth certainly the concept of failing gracefully is fairly widespread in broad technical contexts; whether it's suitable for the mass market is another matter (even outside work much of my time is spent with technical types)
    – Chris H
    Commented Oct 4, 2019 at 13:22

These designs feature inherent utility.

Their design features an intrinsic quality that makes them utile even when they're not fully functional. In fact, you could use the word intrinsic instead of inherent.

These are not standard phrases, but I think are understandable on their faces.

Also consider redundant utility.


Additional answer:

We can also say the design of these devices has a built-in fail-safe.


1 : incorporating some feature for automatically counteracting the effect of an anticipated possible source of failure.

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    I agree with this though I prefer useful to utile as I prefer stink to fetor. :)
    – Lambie
    Commented Oct 3, 2019 at 16:31
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    @Lambie Fetor is a perfectly cromulent word.
    – David M
    Commented Oct 3, 2019 at 16:33
  • I think "inherent" is way difficult to define. Which is more inherent, riding a powered moped, or pedaling a dead one? Redundant would be if there was a second escalator right next to the first one.
    – puppetsock
    Commented Oct 3, 2019 at 16:53
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    @puppetsock I didn't say most inherent. Rather the the utility is inherent to the design, i.e. at its core.
    – David M
    Commented Oct 3, 2019 at 20:46
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    Fail-safe isn't quite right though. Brakes which fail by applying themselves when not required "fail safe", but the car is not usable until the brakes are fixed. Commented Oct 4, 2019 at 10:35

These machines are manually operable.

Assuming one mode as powered by a motor as automatic and a secondary non-powered mode of use as manual such as in the case of escalators or mopeds, all of these items have the same in common. They can be operated manually.


In aviation safety engineering, this is referred to as “Fail Operational”, which is not the same thing as fail-safe. An elevator is fail-safe, but it doesn’t retain any useful functionality when it fails like an escalator does.


Power Independent: The examples you listed are powered, but can still function independently of the intended power source.


In the computer software world, some would call this "service-tolerant". It has a failure, but keeps working at a lesser ability.

Fault-tolerant means it keeps functioning without loss of ability even though there is a fault.

Service-Tolerant means it functions, at a lessened ability, but does not fail because of a fault.

An example would be an expensive high-speed network link that fails and an inexpensive slow network is used instead, transparently to the application using the network link. The job gets done, just more slowly.

Ambiguously, some use the term "service-tolerant" to mean a system can be serviced while it is in operation without shutting the system down.

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    Your suggested answer is one OP has already ruled out in the body of the post - can you explain why you think it's still an appropriate term?
    – V2Blast
    Commented Oct 4, 2019 at 4:05
  • My fingers got ahead of my brain - I meant "Service-Tolerant". I'll make it a diffrent answer
    – Mark Diaz
    Commented Oct 7, 2019 at 22:07

In ecology one says that a system is resilient against acute-stress episodes, and robust against chronic-stress situations. Name 'stress' anything that could impair the integrity or functionality of the system.

This having been said, for day-to-day objects I would prefer the word robust, somehow. I would say that a moped is robust against the lack of fuel, an electric toothbrush is so against the lack of power supply.

Entry 6 in https://www.dictionary.com/browse/robust has a general definition that seems to cover this usage: "strong and effective in all or most situations and conditions"

Disclaimer: not a mother tongue.


Those are items with a manual fallback mode in case of power failure. Fallback generally is a term describing an alternative mode or procedure that can be temporarily substituted when the principal manner of operation breaks down.

  • Fallback suggests some sort of transition. However the given examples naturally provide a manual mode of operation when there is no power. Commented Oct 17, 2019 at 8:42

David M already mentioned 'fail-safe', but I found an explanation that is closely aligned with OP's description:


Contrary to popular understanding, "fail safe" does not mean "safe from failing", i.e. "failure-proof" — it means that if (when) it fails, it will do so in a way that leaves it safe. When something is described as "fail safe", it means that it has been designed and built so that a critical mechanical failure or operator mistake will cause the system in question to default to its safest possible state, quickly and automatically, without any human intervention. Consider the following: if you're at an intersection where there's a traffic light, and it fails, if it "fails safe" then either it goes dark or all four directions show a red signal. If it showed green in all four directions, that would be a failure to fail safe.

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    Can you support your suggested answer by citing some evidence of its definition/use to mean what OP is asking for?
    – V2Blast
    Commented Oct 4, 2019 at 4:04
  • A fail-safe on a railway system say will not allow travel if it comes into operation. Commented Oct 5, 2019 at 14:30
  • Not all fail-safes work the same way. The example given of the traffic light - it still works for intended purpose, but in a modified way. Like a motor bike to a pedaled bike - still provides transportation but in a modified way. Not saying fail-safe is a perfect match for OP's concept - that may require a sniglet. ;-)
    – tblue
    Commented Oct 5, 2019 at 14:59

Power Assisted

I'm not aware of a term that specifically describes this design idiom. But you could safely each of these technologies as power assisted.

Power assisted steering in your car has this same quality. My power steering went out on me in the middle of a sharp turn once. It took some physical labor, but I got home safely. (phew!) So these systems do share a fail safe quality. But I think that isn't the only, or even primary, design goal when building a power assisted technology.

Like mopeds, our modern electric bicycles are another good example.

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    To me this covers a significant class of the examples given. A different word might be appropriate for the other examples.
    – AnthonyVO
    Commented Oct 16, 2019 at 18:39



It is a persistent mechanism in that it continues to function despite being broken.

It also continues to function persistently.


I'm not aware of any existing habitual expression for this concept. If I were to think about inventing a vocabulary for this idea, I'd do something along these lines:

Descriptive phrase: "Useful [or useable] even when not fully functional", or

"Useful [or useable] even when functionally degraded".

Name: "Full-or-degraded functionality machine [or device, or product etc]"

Acronym: "FOD [Full-or-degraded] machine"


100% latently operable

Meaning that it still operates when un-powered or unmoving.

I think that works for scooter, escalator, and toothbrush, and is pretty clear in meaning and not likely to be mixed up with existing jargon or technical terms.

Other options could include 'passively' - ie when not active or powered.

  • fully passively operable
  • 100% passively usable

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