Definition of "nightmare"

It haunted me, however, more than once, like the nightmare.

1817 December 31 (indicated as 1818), [Walter Scott], Rob Roy. […], volumes (please specify |volume=I to III), Edinburgh: […] James Ballantyne and Co. for Archibald Constable and Co. […]; London: Longman, Hurst, Rees, Orme, and Brown

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!

1843, Edgar Allan Poe, The Black Cat

The Night-mare generally ſeizes people ſleeping on their backs, and often begins with frightful dreams, which are ſoon ſucceeded by a difficult reſpiration, a violent oppreſſion on the breaſt, and a total privation of voluntary motion.

1753, John Bond, An Essay on the Incubus, or Night-mare, London: Printed for D. Wilson and T. Durham, at Plato’s Head, in the Strand, page 2

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

1792, James Boswell, in Danziger & Brady (eds.), Boswell: The Great Biographer (Journals 1789–1795), Yale 1989, p. 209

With his crude potato-sack mask and fear-inducing toxins, The Scarecrow, a “psychopharmacologist” at an insane asylum, acts as a conjurer of nightmares, capable of turning his patients’ most terrifying anxieties against them.

July 18 2012, Scott Tobias, AV Club The Dark Knight Rises

If Euston is not typically English, St. Pancras is. Its façade is a nightmare of improbable Gothic. It is fairly plastered with the aesthetic ideals of 1868, and the only beautiful thing about it is Barlow's roof. It is haunted by the stuffier kind of ghost. Yet there is something about the ordered whole of St. Pancras that would make demolition a terrible pity.

1941 August, C. Hamilton Ellis, “The English Station”, in Railway Magazine, page 358

The Red Holocaust is best interpreted in this light as the bitter fruit of an utopian gambit that was socially misengineered into a dystopic nightmare by despots in humanitarian disguise.

2009, Steven Rosefielde, Red Holocaust, page 240

Brother Fary of Omaha was nightmaring the rest of the night.

1931, The Sleeping Car Conductor, page 16

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.

1998, Andrea Benton Rushing, “Surviving Rape: A Morning/Mourning Ritual”, in Mary E. Odem, Jody Clay-Warner, editors, Confronting Rape and Sexual Assault (Worlds of Women; number 3), SR Books, published 2003, page 6

He must be imagining that behind the rain of leaves was a dark-haired man sitting in his chair, smiling away. He must be so fed up with himself that he was nightmaring while awake.

2011, Rachel Simon, The Story of Beautiful Girl, Grand Central Publishing, published 2012