Cassgender is a gender identity where one feels that their gender is unimportant or where one is indifferent to the idea of gender. Cassgender is different from a lack of gender, as a cassgender individual might have a gender but not feel that it's an important part of their identity.
A related term is cassflux, where the level of indifference fluctuates. Sometimes one might feel completely indifferent towards gender, but at other times gender might feel more important.
The term was coined by Tumblr user okaygender via mogai-archive on September 28, 2014.
The cassgender flag was created by pride-flags-for-us on or before February 27, 2015.
"Cass" means "to render useless or void" in English.