Denying the rights of some women and trying to block them from women's spaces makes you a TERF. Allying yourself with Fundamentalist religious hate groups because you share the same transphobia while trying to claim you are doing it for ~feminist reasons~ makes you a TERF.

Being willing to throw any number of women under the bus in the name of sticking it to trans women makes you a TERF.

For any of those things you claimed, context fucking matters.