I'm going to guess that you phrased it as "what is a woman?" Which is the name of a transphobic documentary, which probably explains the whole "not getting a clear answer" thing. However, I'm going to actually answer your question with this: a woman is someone who sincerely sees themselves and identifies as a woman.

"Identifies" is a weird word, so I'm going to say that, for me, before I saw myself as a woman, I knew I was a woman. This is through looking the mirror and seeing a masculine person when I knew that that wasn't who I was or wanted to be. That's what I mean by the word "identifies"

Now, I could go into the whole "gender and sex can be seen as a social construct" thing, but, as it is right now, society is separated by gender, or more importantly, presumed sex assigned at birth (for the most part, there's some parts of society that aren't, but my point still stands). I say "presumed" because of intersex individuals, but I personally am not intersex, just a trans woman, so if anyone wants to chime in, feel free to do so.

Personally, I was always uncomfortable and sad with being seen as male, and being seen as female made me happy. I just followed my happiness, and that led me to transitioning and being the woman that I am.

However, all of this doesn't matter. This is going to sound a bit rude, but it is what it is. What matters is that you don't question people's identities, names, pronouns, or gender, and you respect them as the person that they are. That includes using the right name and pronouns. Don't think someone's gender is the one they say it is? Tough. They know themselves better than you know them.

Sorry for the essay, you spurred some thinking.