Enanteian

Enanteian is being the opposite gender (antigender) of one's assigned gender at birth, or when one's currently identity is the antigender of one's AGAB.

It's similar to contragender, but enanteians aren't essentially against everything or most things that they associate with their assigned gender. Not necessarily like transgender, as a trans person can still experience one's AGAB as a nongender or even eugender when combined with other identities.

The orientation form is called enanteic.