What is the word that describes a word that is used in literature/writing, but not normally in common dialogue?

Solution 1:

I'd go for...

recherche - exotic or obscure.
...or...
recondite - difficult to understand; known only by experts.

...either of which words could reasonably be used to describe the other.

Here are a few hundred written instances of recondite vocabulary to show it is used thus.

For a more common/informal alternative (i.e. - one which imho definitely doesn't "describe itself", OP could always say "recondite" is a highfalutin word (academics don't use that one, so they don't care if it's spelt highfaluten, hifalutin, highfaluting, or whatever).

Solution 2:

You are probably thinking of literary:

4.
a. Appropriate to literature rather than everyday speech or writing.
b. Bookish; pedantic.

It is often used in dictionaries to denote that a word is used more in writing than in normal speech. See, for example, this definition of tartuffe:

noun
literary or humorous

a religious hypocrite, or a hypocritical pretender to excellence of any kind. [from the name of the principal character (a religious hypocrite) in Molière's Tartuffe (1664)]

If you want to be more caustic, you could say that people on this site deliberately use obfuscating language.

Solution 3:

You could use the adjective academic, which has these as definitions:

Learned or scholarly but lacking in worldliness, common sense, or practicality.

Scholarly to the point of being unaware of the outside world.

You could say that something was, for example, an academic point, an academic argument, or an academic question.