I will admit I was stumped by this one. I went in search of a new favorite words starting with X. I found it.
Xanthippe is an ill tempered woman. Taming of the shrew anyone? Yesterday, that described me to a T. Everything around me was uber irritating. The house, the kids, the big kid I'm married to. Nothing pleased me. I was a xanthippe.
So next time somebody calls you a something that starts with B and ends in itch, just tell them you're a xanthippe. It'll shut them up and they'll have to go look it up in the dictionary. And they'll probably look in Z.