Mousegender is a xenogender that feels small, soft or fluffy and it can feel that it may hide or sneak around, or in a way be hidden or hiding. It may feel like it is hiding in a cozy or soft place or also may be a gender that is a connection to mice or incorporates mice to better understand their gender. It is neither masculine or feminine by nature but can be used by those who lean masculine or feminine. It is a faunagender and may also be a kingender.
An alternative meaning by u/IWriteALot2 is a gender that feels small and soft like a mouse or is connected to mice in some way.
Mousegender was coined by Tumblr user Meowdy on December 23rd, 2018. Bun-gender's alternate flag design was created on August 24th, 2021, intended to be a more modern design and better representation of being mousegender.
The meaning of the original mousegender flag is unknown.
Bun-gender's alternate flag design has a meaning that was attached in the original post: Brown represents other members within the rodent family. Light brown represents softness and gentleness. White represents a unique connection to gender. Light grey represents a sense of stealth, and the feeling of hiding away. Regular grey represents a generic color of mice fur and mice as a whole.
Lilsillymouse's flag was posted here in the comments, on March 23rd 2021 with no meanings listed