Anonbinary is a gender that isn't binary, but even still, is outside of non-binary. It uses the prefix a- to show this, although it is not necessarily the same as agender. The difference being that agender is the lack of any gender. Anonbinary people have a feeling of gender, but that gender is not a binary or non-binary gender. Anonbinary can be a gender identity on it's own or it can be used as an umbrella term. Some anonbinary people may also identify as transgender.
Anonbinary can include genders (such as xenogenders) that aren't defined how they relate or don't relate to the gender binary.
Anonbinary people can have any sexual orientation. Some may use the anonbinary collection of sexualities.
History
The term anonbinary was coined by an anomynous through pride-color-schemes on June 19th of 2017.
Flag
The flag was coined by Mod Hermy through tumblr user pride-color-schemes account on June 19th of 2017. It has no confirmed meaning.
Resources
https://pride-color-schemes.tumblr.com/post/162002891990/anonbinary