What is a nightmare in the daytime called?

Sorry no punchlines, serious question. And more importantly, how the fuck do they occur?
I had one today, and it scared the shit out of me, I must have been pretty fucking out of it because when I came to the girl next to me was hugging me.
Apparantly my eyes were really dilated and my arm kept shaking. Had the same nightmare last night attempting to sleep.
Probably won't happen again, but anyone else had this occur?
I had one today, and it scared the shit out of me, I must have been pretty fucking out of it because when I came to the girl next to me was hugging me.
Apparantly my eyes were really dilated and my arm kept shaking. Had the same nightmare last night attempting to sleep.
Probably won't happen again, but anyone else had this occur?