A frightening nightmare.
Person A: Did you sleep well last night?
Person B: No, I had a frightmare and woke up drenched in sweat.
(noun): Originated by "1000 Ways To Die". A frightmare is when you have a repeated nightmare and you die in your sleep from a heart attack.
Tina told me that she use to have nightmares about midgets. That's before she died in her sleep from a frightmare.