Just don't say it out loud around Granny Weatherwax, since she's prob'ly the midwife who delivered that man when he was very young, and the mother wasn't male either. We all get along just fine as long as the women have things their way, and the men have things their way too - the women's way, that is.
No one has the bad taste to comment on this arrangement until Eskarina is born, and a wizard makes a silly mistake. Could happen to anyone really - his dying moments unwittingly infuse the baby girl with wizardly, male magic.
In time, this brings the wrath Mistress Esmeralda Weatherwax down on the fortress of male magic, which is invaded and defeated never even knowing it was engaged. Saves a lot of work and running aroung that way, y'know. But Esme's real problem is that little girl, and her real problem is a little boy, and his real problem is -- unreal.
Neither the womanly witches nor the male mages are quite ready for this little girl with tomboy magic. Nor is she quite ready for herself.
As in Pratchett's other tales, the fun is in the telling. This battle of the sexes, like so many others, is fought to a draw - there will be cultural exchanges, visiting rights and such, and jittery kind of peace. All end up happy enough, but it's still one world with two peoples in it, male and female.
Except maybe for that girl and that boy. Male and female yes, in a child's way, but they have much too much in common.
Dying wizard Drum Billet eagerly passes his magic staff on to a newborn wizard - the eighth son of an eighth son. Unfortunately, in his rush, he failed to notice the child was a girl. Unwittingly, Billet is responsible for the first ever female Wizard in Discworld.
All, including Granny Weatherwax (a witch) try to ignore the event, but neither the magic staff nor little girl Esk will let them.
Esk grows up amidst her brothers, but when she's nearly nine, a frightening incident involving Granny opens the flood gates to her magic abilities. Granny decides it is time to teach Esk to become a witch, in the hope that her wizardness can be squashed.
Of course, this proves impossible, and soon Granny and Esk need to embark on a journey to the Unseen University of Wizards. Esk finds that the chauvinistic wizards are unwilling to entertain the notion of a female wizard. But a nine-year old little girl and a cranky granny can be more than a determined handful ...
The character of Granny reappears in later Discworld books and she is an absolute delight: a stubborn witch with more that the average share of common sense - well, mostly anyway.
The genius of Pratchett is that you don't even notice how quickly you are willing to accept Discworld and its characters. Before you know it, this little cocoon of enchanting surreality is over.