Alex Byrne contends that women are (simply) adult human females, claiming that this thesis has considerably greater initial appeal than the justified true belief (JTB) theory of knowledge. This paper refutes Byrne’s thesis in the same way the JTB theory of knowledge is widely thought to have been refuted: through simple counterexamples. Lessons are drawn. One lesson is that women need not be human. A second lesson is that biology and physical phenotypes are both irrelevant to whether someone is a (...) woman, and indeed, female in a gendered sense. A third lesson is that trans women, cis women, alien women, and robot women are all women because to be a woman is to be an adult gendered female. This paper does not purport to settle complex normative questions of ethics or justice, including whether the ordinary meaning of “woman” ought to be retained or changed—though I do note plausible implications for these debates. This paper does purport to settle what the ordinary meaning of “woman” is, and in that regard contribute to important conceptual ground-clearing regarding what constitutes an ameliorative or revisionary definition of “woman.”. (shrink)