What is a woman? 'Woman' is only a word that humanity has defined as what roles and features most biological women have dominantly. But only most of them have those features and accept those roles and this word can be defined differently in every culture.
So 'woman' is only a word that describes most biological females and not all of them. In contrast, it is the same for the word 'man'. But any biological man or woman can define him/herself as each of these two words based on his/her gender identity that has formed in his/her mind in early age.