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 individual 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, when being undefined is its main quality. It's often used by individuals who cannot narrow down their gender any more than being unidentifiable.
The creator of the original flag is IMOGA-Pride on Tumblr on January 13th, 2019.
An alternate version of the flag was created by Jeb_CC, designed to symbolize the undetermined aesthetic in a more obvious manner. Both halves represent the unknown nature of the sea and space.