Good on you for giving this a go, SpookyFBI. I take back my earlier tacit implications about your lack of good faith.
I think others have taken on the 'adoption' and 'stepmother' analogies; it is a well known move. Just one thing to add here: 'stepmother' means 'a woman who has married one's father after one's mother's death or divorce'. That is a straightforward non-circular explanation of what 'stepmother' means; is anything similar available regarding the meaning of 'woman' in the context of an assertion 'TWAW'? If so, what?
The main thing to note, though, is the difference between "the meaning of 'woman'" and "what it means to you to be a woman." You try to tell us something about the latter, when what you were asked for is the former. But they are not the same. And it is the former we need if we are to begin to make clear sense of what 'woman' means in "a trans woman is a woman" so we can assess this latter assertion for truth or falsity.
This is tricky, I know. One way to keep the difference in view is to notice - and keep in mind - the difference between a woman (a kind of human being, we will all agree, at least), and 'woman' (a word). (Check out the quote-marks.)
[This is a distinction I was signalling when in an earlier post I mentioned "material mode". Let's not overdo this: by all means, if you're interested, look up the difference between material and formal mode; or equivalently the use/mention distinction. But we should be able to understand what is going on without over-egging such technical notions.]
Look, we know you think, in some way, that TWAW. I think you are wrong to think that. I think it cannot be true that TWAW. But if we only consider what being a woman means to you, we will not be able to move on from that to see whether 'TWAW' is true or not, because part of what being a woman means to you is, of course, that TWAW (which is equivalent to saying "'TWAW' is true"). And we get nowhere in our discussion if we assume what we want to argue for in the premises of our argument.
Yes, this is tricky. One way out of the difficulty, I think, is to focus on the question I posed (and try not to paraphrase it into other terms that may only seem to be its equivalent). If you can't answer it simply and clearly, ask yourself why not.
Can you say what 'woman' means in the context of an assertion 'TWAW'?
-- Again, a popular explanation of the meaning of 'woman' is ruled out by that assertion: if 'woman' means 'adult female human', a trans woman cannot be a woman. So how are you going to get 'TWAW' to come out true? What other meaning (you must offer some other meaning if you are sincerely asserting it) can you offer?
What it means to you to be a woman is not at all relevant to this. Do you see?
[And one last thing: "... everyone should feel liberated to define themselves in whatever way works best for them" might work for people (though really I am unsure what it might mean to define oneself in any substantive way). It cannot work for words, though: remember Humpty Dumpty:
“When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean — neither more nor less.’
’The question is,’ said Alice, ‘whether you can make words mean so many different things.’
’The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.”
--To be clear, this was a (logico-semantic) joke by Lewis Carroll (or maybe by Charles Dodgson). Alice was right to be sceptical.]
Thanks for getting me to think about this by exposing your own thoughts the way you have, SpookyFBI. It is interesting to see where thoughts like yours come from. I hope that doesn't sound too patronising. Anyway, I'm glad you enjoy motherhood.