This question applies primarily to coding. Is there a term that describes input that is valid but unusual?

For example: If I ask for a username, and get @##3i7&*(x]. The code should allow this, but it's not within the realm of expected, username-like inputs.

A similar real life example: going to a restaurant alone and ordering 6 of the same appetizers and a bottle of wine. This is allowed, but abnormal.

The word "strange" comes to mind, but that doesn't feel technical enough.

Thanks for the help!

  • What's wrong with "unusual"? The term makes no judgment about validity, only frequency of occurrence.
    – Robusto
    Sep 10, 2015 at 16:47
  • 3
    I like "unconventional" here.
    – DyingIsFun
    Sep 10, 2015 at 16:49
  • +1 for unconventional. "Peculiar" is another possibility..
    – Graffito
    Sep 10, 2015 at 16:52
  • 1
    Or eccentric, unexpected, odd. Sep 10, 2015 at 17:09
  • 1
    @##3i7&*(x] is an outlier. Sep 10, 2015 at 19:16

3 Answers 3


We typically refer to such cases (of atypical, bizarre, or exceptional use cases, including user input) as corner cases.

  • Labelling 'going to a restaurant alone and ordering 6 of the same appetizers and a bottle of wine' a 'corner case' could be considered even more bizarre. Sep 10, 2015 at 21:47
  • @EdwinAshworth: Not if you are sitting in the corner. ;-) (I assumed the question, as indicated, "applies primarily to coding".)
    – Drew
    Sep 10, 2015 at 21:52
  • Yet another case of a question with conflicting messages. Sep 10, 2015 at 21:54
  • @EdwinAshworth: You're right. I didn't even bother with that part of the question. Maybe it should be closed as unclear.
    – Drew
    Sep 10, 2015 at 21:56
  • I've just attacked the upvote. As I often find myself doing. Sep 10, 2015 at 21:56

Three terms immediately occur to me:
1. Unconventional.
2. Atypical.
3. Unorthodox.

But these are just regular words prefixed with negative modifiers.

I also like:
4. Eccentric.

And particularly applicable to programming:
5. Idiomatic.

FYI: In a CLI context, I most often observe very brief, simple messages such as "Unexpected Argument.." If you're concerned about your own ambiguity and potential for being misinterpreted; try using colours and/or symbols, such as [ - ] & [ + ] ...


I'd say "sui generis", "unique" or "peculiar".

  • sui generis (adj) Sui generis is a Latin term meaning 'forming a kind by itself; in a class or group of its own : not like anything else

  • unique (adj) used to say that something or someone is unlike anything or anyone else

  • peculiar (adj) characteristic of only one person, group, or thing : distinctive

source MW

e.g. "a unique ball-point pen", "a most peculiar username", "his project is sui generis"

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