> I'd have assumed "sexual" meant relating to sex (intercourse), rather than relating to sexes (male/female)

No, sexual harassment is any form of it that references the sexes (male/female), otherwise garden variety misogyny (e.g. "women are bad at X", "X is bad at Y, because she's a woman") wouldn't be considered sexual harassment.

But "women are bad at X" is not 'sexual harassment'.

Misogyny is not identical to sexual harassment, they are two different things with some overlap.

EDIT: would downvoters (or downvoter + socks) like to explain their disagreement? I'm happy to be corrected.

Not sure why you're getting downvoted. The statement has nothing to do with anything sexual. Unless "sexual harassment" has lately been redefined to mean "harassment based on sex"

Saying "women are bad at X" isn't necessarily sexual harassment; It's just misogyny. But if you said it to a woman, it would be sexual harassment.

There's a difference between sexual behaviour and gendered insults, that's my point. Or no?