nightmare

A very unpleasant or frightening dream.

• I had a nightmare that I tried to run but could neither move nor breathe.

Any bad, miserable, difficult or terrifying situation or experience that arouses anxiety, terror, agony or great displeasure.figuratively

• Cleaning up after identity theft can be a nightmare of phone calls and letters.

A demon or monster, thought to plague people while they slept and cause a feeling of suffocation and terror during sleep.archaic

• It haunted me, however, more than once, like a night-mare.
• I started, hourly, from dreams of unutterable fear, to find the hot breath of the thing upon my face, and its vast weight—an incarnate Night-Mare that I had no power to shake off—incumbent eternally upon my heart!

A feeling of extreme anxiety or suffocation experienced during sleep; sleep paralysis.historical

• Had been afflicted in the night with that strange complaint called the nightmare.

To experience a nightmare.intransitive

• Brother Fary of Omaha was nightmaring the rest of the night.
• It’s been 21,900 hours, 912 days, 130 Saturday nights, 30 months, 3 years since October 16, 1988 when I was stunned awake, straddled by a man I did not know. First I think I’m nightmaring.

To imagine (someone or something) as in a nightmare.transitive

• She was the last person I’d expected to see, although I had not expected to see anyone at all. For a moment I thought it was a nightmare, and that I was nightmaring the whole thing.
• Stars have no need of intimidation, which makes them mightier than all the godheads nightmared by mere humanity.

To trouble (someone or something), as by a nightmare.transitive

• THe day is broke! Melpomene, be gone; / Hag of my Fancy, let me now alone: / Night-mare my ſoul no more; Go take thy flight / Where Traytors Ghoſts keep an eternal night; […]
• Thou things imponderable dost price and weigh / By scales untrue ’gainst the gewgaws and gauds / O’ the World; thy ledger ’neath thy head dost lay / For pillow, nightmared with dreams of thy hoards.