F&M
You tell someone something, and they end it with 'F or M?' to make you feel like an idiot. It's like they're saying, 'You're dumb, and you're either a boy or a girl.'
I told him my life story. He said, 'F or M?'
She told me about her dog. I said, 'F or M?'
He explained quantum physics. I said, 'F or M?'