When someone states that one is a gender other than one identifies. Misgendering is most common when it comes to transgender individuals, but can happen to cisgender people as well. (Example: Being called "Sir" when "Ma'am" is appropriate, etc...)
The act of offending a narcissist by failing to intuit, guess, or otherwise predict and align with their own delusional view about which sex they are.
"You see that person over there with his cock and balls on show?"
"Yes, who is he?"
"Don't misgender her you transphobic Nazi who's worse than Hitler!"