Agender X is an umbrella term for people who are agender or genderless, yet are still aligned to a certain gender. The "X" can be replaced by any gender term.
For example, an agender girl is genderless, but may consider themself aligned to girlhood because they have experiences similar to a girl's. For example, experiencing misogyny, and using the ladies' bathroom.
It is similar to terms such as boyprox and girlprox. However, these terms do not specify the person's gender.