From their "guide":
"A woman is someone who identifies as a woman. Many women are cisgender (often written as cis), and this means the gender they were assigned at birth matches their gender identity. Some women are transgender (often written as trans), and this means that the gender they were assigned at birth didn't match their gender identity.
Cis women and trans women are women – it’s as simple as that."
Circular meaningless nonsense. A woman is someone who identifies as a woman.... what is a woman, someone who identifies as a woman... yes, but what is this thing "woman" that they identify as....well, is is someone who identifies as a woman... and on and on and on and on into an endless spiral, void of meaning and use.