Well, it depends what “trans” means.
First, cis means not trans, as in trans-lunar or cis-lunar (this side of the moon), or cis-trans isomerism in organic chemistry; and not trans as in cis woman. The term prevents people othering us. Unless it is relevant, refer to a “woman” or a “person”- if trans status is really relevant, women are cis women or trans women. The only alternative is some variation of real v fake, or normal v queer. Yes you are a woman, but some are more woman than you– whether because they menstruate, or because of their upbringing, or for some other criterion you cannot possibly fulfil. Or, you are not a woman.
Cissexual has a clear meaning. It means someone has not physically transitioned from one sex to the other- though some deny that is possible. Someone who has not had SRS, then, and does not want it- because I was transsexual before my operation, because I wanted it. Cisgendered is more difficult. Everyone breaks gender rules. No-one is happy with all gender stereotypes. We express different parts of our personalities at different times, and when in purely professional role might be agendered, as in the moment of a doctor performing a physical examination. The doctor is still a man or a woman, but that does not matter.
If cis means “not trans”, then if we want a big tent, to include and affirm as many potentially trans people as possible, it becomes more difficult to say someone is definitely excluded, because everyone is redefining and influencing gender roles. Roles do not stay the same, not even “Biblical” understandings of gender roles, but are continually reinterpreted.
And yet if “cis” does not have a precise meaning, it still has use as a generalisation. If someone does not identify as trans, then calling them cis is no insult. Some of us fight gender stereotypes in this particular way. No radical feminist denies she is a woman.
None of this is clear cut. It resists clear definitions. I was rebuked for using the word “transsexual”- it implies that you need to have, or want, surgery to be proper trans, she said. Well, I want the big tent, and no-one should be required to undergo sterilisation before they can have gender recognition; but she can assert that without disparaging or erasing my experience. We are trans in different ways. No-one’s way of being trans means that some other way is impermissible or inauthentic. And no-one should disparage other ways of being trans, in an attempt to be accepted. Some cis people accept trans people, and some cis people do not; but no cis person imagines that one way of being trans is acceptable and real and other ways are not.
I started on this line inspired by Julia Serano again, but have gone off on my own line. She is worth reading. It is my current intention to blog again on 31 August, though it is possible I will before then.