I'm having a hard time thinking of an example, except I remember someone making a recursive joke about it once. They explained the meaning of it by using its definition, hence the joke. Something like "An X is only an X for those who already know".

What is the name for this kind of phrase?

  • 7
    Your question is severely underspecified.
    – Jim Balter
    Mar 21, 2017 at 8:32
  • 26
    @JimBalter not necessarily undespecified. If you knew what he is talking about you'd know what he is talking about.
    – xDaizu
    Mar 22, 2017 at 13:18
  • 1
    @MattThomas actually my comment was a recursive joke based on your own question.
    – xDaizu
    Mar 22, 2017 at 13:24
  • Don't post answers in the comments.
    – Kit Z. Fox
    Mar 22, 2017 at 13:26

12 Answers 12




  1. a custom, phrase, or use of language that acts as a test of belonging to, or as a stumbling block to becoming a member of, a particular social class, profession, etc


Today, in American English, a shibboleth also has a wider meaning, referring to any "in-group" word or phrase that can be used to distinguish members of a group from outsiders – even when not used by a hostile other group

Probably not what you're looking for, but a fun word nonetheless.

  • Comments are not for extended discussion; this conversation has been moved to chat.
    – tchrist
    Mar 25, 2017 at 19:23



1. understood by or meant for only the select few who have special knowledge or interest; recondite:

2. belonging to the select few.

3. private; secret; confidential.

4. (of a philosophical doctrine or the like) intended to be revealed only to the initiates of a group

  • 3
    I don't think this is the word I was looking for, but it probably answers my question (as worded) best. Thanks Mar 20, 2017 at 20:02
  • 1
    The community voted. Sorry, Ricky, but I think I need to change accepted answers Mar 23, 2017 at 14:06
  • 1
    Sometimes the community is wrong (actually, it is probably right in this case, but I believe esoteric would be easier to understand in most cases where the readers may not be "in the know"). Mar 23, 2017 at 14:38

The question in your title doesn't really match what's asked in the body of your question. But a possible answer to the question in your title is jargon.

special words and phrases that are used by particular groups of people, especially in their work

The Wikipedia entry for jargon adds to this by saying

The main trait that distinguishes jargon from the rest of a language is special vocabulary—including some words specific to it and, often, narrower senses of words that outgroups would tend to take in a broader sense.

In other words, jargon can include words whose meaning within a group is quite different than the meaning outside that group.


Perhaps you are remembering the somewhat recent use of the term dog-whistle. From Oxford Dictionaries:

1.1 usually as modifier A subtly aimed political message which is intended for, and can only be understood by, a particular demographic group.

There's a fair bit of discussion about the origin of this particular usage in this EL&U question and its answers. (Essentially, it's a metaphor from actual dog whistles, which are so high-pitched that only dogs can hear them, originally applied to politics in Australia and very quickly adopted throughout the English-speaking world.) This phrase came up a lot during the recent political turmoil in the UK and US.

  • 1
    I actually haven't heard the term before—thanks for the new phrase! Mar 20, 2017 at 21:20
  • 2
    @MattThomas One can infer that you don't read liberal political commentary.
    – Jim Balter
    Mar 21, 2017 at 8:18
  • @JimBalter These days my head is mostly buried in software and technical documentation :| Mar 21, 2017 at 12:25

In the 19th century, the parlance of criminals in the UK would be termed argot, the word is less popular these days but still relevant and has a broader usage.

Wikipedia defines it as:

An argot (English pronunciation: /ˈɑːrɡoʊ/; from French argot [aʁˈɡo] 'slang') is a secret language used by various groups—e.g., schoolmates, outlaws, colleagues, among many others—to prevent outsiders from understanding their conversations. The term argot is also used to refer to the informal specialized vocabulary from a particular field of study, occupation, or hobby, in which sense it overlaps with jargon.


term of art


a word or phrase that has a specific or precise meaning within a given discipline or field and might have a different meaning in common usage:

Set is a term of art used by mathematicians, and burden of proof is a term of art used by lawyers.


You could make a self-referential joke like this for example:

"Term of art" is a term of art in the legal profession.


The phrase is self-referential, and you're indicating a case of self-referential humor.

Self-referential humor or self-reflexive humor is a type of comedic expression1 that—either directed toward some other subject, or openly directed toward itself—intentionally alludes to the very person who is expressing the humor in a comedic fashion, or to some specific aspect of that same comedic expression.

These are variants of Hofstadter's famous recursive-acronym, which is very influential in the computer-science domain. For instance, GNU is a recursive acronym for GNU's Not Unix.

  • 1
    My attempted example was definitely self-referential, but this doesn't quite fit: self-reference does not imply a lack of understanding Mar 20, 2017 at 20:06
  • Ah, okay, I missed the point of that.
    – jimm101
    Mar 20, 2017 at 20:07

You might be talking about a code name (sometimes code word or code phrase):

  1. Also called code phrase. a word or phrase assigned a meaning understood only by those who are secretly informed of it.

Popular in spy movies, these are words or phrases that sound otherwise innocuous, but indicate to the listener that you are "in the know".


It sounds like the situation you're describing is a circular definition. wikipedia

A circular definition is one that uses the term(s) being defined as a part of the definition or assumes a prior understanding of the term being defined.

And, long-shot, but maybe you were talking about an "autological word" wikipedia again

An autological word (also called homological word or autonym) is a word that expresses a property that it also possesses (e.g. the word "short" is short, "noun" is a noun, "English" is English, "pentasyllabic" has five syllables, "word" is a word).




  1. needless repetition of an idea, especially in words other than those of the immediate context, without imparting additional force or clearness, as in “widow woman.”.

  2. an instance of such repetition.

  3. Logic. a compound propositional form all of whose instances are true, as “A or not A.”. an instance of such a form, as “This candidate will win or will not win.”.

  • 1
    Not even close.
    – Jim Balter
    Mar 24, 2017 at 14:18

Is this the first documented example of the theoretical phenomenon first hinted at by D. Rumsfeld (DR)?

Ref ...there are known knowns etc

While the focus for DR was unknown unknowns, this gave a tantalising suggestion of the possible existence of something more esoteric and exotic, an unknown known. I.e. something where you may or may not have some intuition it exists, but that you cannot detail it with any plausible specificity.

  • 1
    Unknown knowns are possible. For instance, you might know your neighbor's shoe size but not know that you do because you're unaware that the person whose foot you measured today in your shoe store is your neighbor.
    – Jim Balter
    Mar 24, 2017 at 14:15

Can I suggest it is an instance of Hermetica. I.e. in the sense used by Umberto Eco in Foucault's Pendulum.

The Hermetica are Egyptian-Greek wisdom texts from the 2nd and 3rd centuries AD, which are mostly presented as dialogues. Ref Hermetica

So, in Eco's Foucault's Pendulum, according to an authoritative opinion, it's a joke at the expense of the hermetic characters the publishers spend much of their time with, as when it's first used it's about how they literally all have a certain look about them (Lorenza says "professional sorcerers with faces exactly like professional sorcerers", then describes them. Diotallevi quips "Facies hermetica", and from then on it's an in-joke). Ref goodreads.com/questions/463533...

  • Please include a definition of this word and describe the sense it is used in in Foucault's Pendulum.
    – Kit Z. Fox
    Mar 27, 2017 at 12:51

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