Someone with no Y-Chromostome. It is really as simple as that. Lia Thomas, it is a free country and I will be polite and call you a she if you'd like, but a $30 23&me test will show you have the male chromosome, and thus are biologically male.
For intersex people, if they have a functioning female reproductive system and naturally have their testosterone/estrogen ratio within X many standard deviations of the female average, then the presence of a Y-chromosome is an anomoly from the female body, as opposed to the inverse. As such, I suppose they could be classed as female too. Obviously, one set of sexual characteristics is going to be naturally more dominant than the other.