When something works, but it is unreliable and intermittently goes wrong, what could it be called?

I'm actually thinking of computer software. In my work we tend to use the word "flakey", but there must be a better one.

  • Thesaurus entry for flaky, unreliable
    – user2512
    Jul 15, 2011 at 12:24
  • 1
    Capricious and mercurial are appropriate when the personifying the system.
    – Mitch
    Jul 15, 2011 at 14:28
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    Unstable is not the best for all connotations, but can be applied in some of the same situations as flaky meaning unreliable.
    – Mitch
    Jul 15, 2011 at 14:29
  • 2
    What about "software" :-)
    – Ian
    Jul 15, 2011 at 16:15
  • 1
    I've always called it "intermittently failing." :-) Jul 15, 2011 at 16:20

9 Answers 9


You are already using the perfect word for unreliable software. According to The New Hacker's Dictionary

flaky /adj./

(var sp. 'flakey') Subject to frequent lossage. This use is of course related to the common slang use of the word to describe a person as eccentric, crazy, or just unreliable. A system that is flaky is working, sort of -- enough that you are tempted to try to use it -- but fails frequently enough that the odds in favor of finishing what you start are low. Commonwealth hackish prefers dodgy or wonky.

If you want to know what lossage, dodgy, or wonky mean, you'll need to follow the links. Following wonky gives you more synonyms.

  • I was going to suggest "wonky" but you beat me to it. "Flaky" is better applied to people, "wonky" to inanimate objects.
    – The Raven
    Jul 15, 2011 at 13:57
  • 1
    But isn't a donkey a 'horse gone wonky'? Jul 15, 2011 at 14:16

Try "unreliable".

  • 1
    I used that word in my question. I suppose it works, but it just seems a bit vague to me.
    – Urbycoz
    Jul 15, 2011 at 13:26
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    I initially thought the same thing, but I think it depends on OP's situation. If his software works or doesn't work, e.g. a web server that sometimes fails to return a page, I'd say "flaky" or "unreliable". If his software seems to always be available but sometimes gives the wrong answer (e.g. a GPS), that's definitely "unreliable". If in his situation "unreliable" could mean that, I might steer away from that word for the case of "sometimes doesn't answer". Of course, I could be over-analyzing this. :-) Jul 15, 2011 at 14:32

Personally I like

Fickle: likely to change, especially due to caprice, irresolution, or instability; casually changeable.

Edit: That is according to Dictionary.com

  • +1 for fickle, a favorite word of mine. It looks like you are citing from a source, but you've not included it. If that's the case, please edit your answer to include the source (and a link, if there is one). If it's commonly used, our list of abbreviations may be helpful. Thanks!
    – Kit Z. Fox
    Jul 16, 2011 at 1:32

Sporadic is also a good word for this

  • 7
    The software would not be sporadic, but it could have a sporadic bug, or there could be a sporadic glitch in the system.
    – jimreed
    Jul 15, 2011 at 16:45
  • something could also be sporadically rewarding, so the usage is un unambiguous Aug 12, 2013 at 18:03

I like the phrase on the blink, which means that it is not working properly. I like the "blink" part in particular, because it implies some intermittent function.

A related phrase is on the fritz, but I've never been entirely sure whether that's offensive or not.

Edit: I agree with the comments on this answer that these phrases would have the implication that the software had been working, but now does not function properly.

  • 4
    To me "on the blink" seems to always imply that it WAS working, but has now stopped working.
    – Urbycoz
    Jul 15, 2011 at 13:28
  • Both these seem to me to mean 'not working at all' rather than 'working sometimes, but sometimes not'
    – Mitch
    Jul 15, 2011 at 14:26
  • 3
    I would say it would mean "this was formerly/normally reliable, but has entered a state where it works only intermittently"
    – Random832
    Jul 15, 2011 at 17:04

Sofware that is unreliable is sometimes called buggy.

  • 1
    But buggy can mean a lot more things than just unreliable/flakey. For example if you consistently can't print a report when it has an odd number of pages, then that's buggy. But it's not really unreliable/flakey. An application that just crashes twice per hour with no visible reason or pattern is unreliable/flakey. Jul 15, 2011 at 12:35
  • 2
    And may be exhibiting a heisenbug :-)
    – jaybee
    Jul 15, 2011 at 13:12
  • @ Jaybee. Nice word. I'll have to remember to use it.
    – Urbycoz
    Jul 15, 2011 at 13:29

Intermittent faults are the bane of an engineer's life.

We can describe physical components as 'intermittent', but I wouldn't regard software as intermittent.

Software should behave deterministically. If software's behaviour is unpredictable, there may be external factors we're unaware of.

In that case, I would definitely go with unreliable and explain it by phase of the Moon effects, if necessary.

  • 3
    Software vaults can easily seem intermittent. I've seen bugs depend on the behaviour of other users on the same server. To the end user that makes the code seem highly non-deterministic. Jul 15, 2011 at 12:41
  • Yes, but it's only an impression of non-determinism. The CPU will execute the same instructions the same way each time unless something external affects it. The software's unreliable because of the conditions under which it's run. But this is all peripheral to the OP's question.
    – pavium
    Jul 15, 2011 at 12:46
  • Physical components are also deterministic. The appearance of non-determinism in either physical components or software stems from an observing human's inability to account for all the relevant inputs. Jul 15, 2011 at 16:25
  • @Karl: Electronics are not completely deterministic, since thermal noise is truly random.
    – Ben Voigt
    Jul 15, 2011 at 18:41
  • @Ben, as far as humans are able to comprehend. At some point there is a physical process that is completely predictable if you could know all the inputs. Jul 15, 2011 at 19:00

I've always thought occulting would be a good term, but it has not yet gathered enough fans to be recognized. Strictly, it refers to lights (usually in lighthouses) that are lit for longer than they are dark (flashing is the opposite), but it has a connotation of the black magic that we all know is really responsible for the bug.


If it keeps running, but occasionally does weird things, one possible word for that would be glitchy (although it would be a more common phrasing to say it has a glitch).

If instead the sporadic bug(s) causes the program to crash (where "crash" in this case means cease executing in an uncontrolled way), a more proper thing to say that the program itself is unstable.

A third possibility is that the bug causes program goes off into an infinite loop. In that case, neither of the above is quite right. There are a myriad of words for this. Probably the best understood would be to say the program locks up. For more similar terms, I generally suggest consulting FOLDOC.

However, you should realize that none of these terms really have precise meanings. The problem is that everyone uses software (and thus needs to use terms like this to describe system behavior), but few people are actual software engineers familiar with the common uses of the jargon.

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