Corugender, or flashgender, is a gender identity in which ones gender is affected by a person's PTSD or other conditions that cause flashbacks. This term is used to express a person's experience with how their gender changes during and around flashbacks. This term is not intended to describe a solitary gender itself, it is used to describe the experience with how a person's gender changes.
For example, a person who is currently female may have a flashback, and for the duration of that flashback experience they will be a demigirl, possibly because that's what gender they were when first experiencing the traumatic event.
This term is typically used by people with PTSD to express how their neurodivergent experiences affect their gendered experiences. Some people use it to express how they believe their gender is affected by past lives, but this is considered a gross homogenization of the experiences of people with PTSD and other conditions.