I mean, of course I've looked it up, and I nod along whenever anyone describes me as cis.
But I don't really know what it means. I am a woman. I experience the world as a woman. I look like a woman and I am happy to be described as a woman. I could not be described as a tomboy. I support women's rights and equality.
But I wouldn't say I 'identify' with the female gender. I find it quite constraining and oppressive. But I would say I am a woman. Am I cis? Am I not? I don't understand!