It occurs to me that we can use 彊 to mean "a completely unknown concept that cannot be named". For example if you ask, "when Cthulhu rises from its slumber, what is thefirst thing it will do? Probably it will 彊.

▲

mkehrt a minute ago | parent | next [-]

So www.catb.org/~esr/jargon/html/M/mu.html

▲

arcanemachiner 4 hours ago | parent | prev | next [-]

That's not on my keyboard... Can I just stick with "ineffable"?

▲

holdupagain 3 hours ago | parent [-]

Not exactly, it doesn't look like the definition or even connotations of "ineffable" include "unknown".

	▲	speerer 2 hours ago \| parent [-]
		It does in the sense that ineffable things are unable to be described in language (conceptually: unknown to language).

▲

9dev 2 hours ago | parent | prev [-]

More mundanely, you could also use it as a marker character, given that nobody except for sneaky little QA hobbitses will ever use it in their input.