And if they throw it that question back at you, you can easily define men and women without stereotypes (and hopefully these definitions takes care of gotchas like 'what if a man lost his dick in an accident, is he still a man?')

A woman is a human female who has breasts that will be able to, can or have in the past, produced milk. Their bodies have or have had a uterus, and can (or had the capacity to) produce eggs. Women are also born with sex specific genitalia, such as the vulva, clitoris and cervix, which may or may not have been removed.

A man is a human male who have chests that do not produce milk; those who do are a minority and anomaly. Their bodies have a prostate, and can (or had the capacity to) produce (viable) sperm. Men are also born with sex specific genitalia, such as the foreskin, penis, and testicles, which may or may not have been removed.

Even if certain parts of their bodies cease to function, or do not function properly, humans are regardless born with sex-specific organs and features. People with intersex conditions should not be used as examples of a third/inbetween sex, as it is not true and I believe quite damaging to public perceptions of people with intersex conditions. They are not your wildcards.

Hopefully this is the best way to describe men and women and there's nothing there that can be refuted.