The original definition of Erisian is a gender that is a combination of lunettian and mercurian. It is also known as merlunettian. An erisian person may feel both at once or they may be fluid between them. They may feel different amounts of each gender at different times.
Under the rework of the celestial gender system, erisian is defined as a gender that is plutoian, lunettian, and mercurian. Someone who is erisian may feel all genders at the same time, feeling a connection to soft feminine energy, soft gendered energy, as well as a connection to the void, or they may be fluid between them. They may feel different amounts of each gender at different times. Erisian can also be considered the demigender form of venusian.
The term erisian and the flag were created by Tumblr user Juparian on December 31, 2017. However, the definition of many of the celestial genders was altered in a rework of the celestial gender system by Tumblr user System-Lgbt designed to make it more consistent. The colors of the new flag are based on the colors of Eris.