Uingender

Uingender is an umbrella term for any genders that are unknown, unnamed, undecided, unsure, undefined, unidentified, unquantifiable, unexplainable, or undetermined in nature (UIN).  It is not the same as questioning, as an uingender person can be certain in the fact that their gender is unidentifiable or unknowable. Uingender does not have to be a temporary state, and they do not have to be looking for to understand their gender.

It can also be used as a gender on its own, referring to any gender isn't fully unknown or undefinable, but its undefinably is is its main feature. It's often used by people who cannot narrow down their gender any more than being unidentifiable.