nightmare
Americannoun
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a terrifying dream in which the dreamer experiences feelings of helplessness, extreme anxiety, sorrow, etc.
- Synonyms:
- phantasmagoria
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a condition, thought, or experience suggestive of a nightmare.
the nightmare of his years in prison.
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(formerly) a monster or evil spirit believed to oppress persons during sleep.
noun
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a terrifying or deeply distressing dream
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an event or condition resembling a terrifying dream
the nightmare of shipwreck
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( as modifier )
a nightmare drive
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a thing that is feared
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(formerly) an evil spirit supposed to harass or suffocate sleeping people
Usage
Where does the word nightmare come from? Nightmares are scary and unpleasant. But you can rest easy knowing that the fascinating origin of the word nightmare makes it clear humans have been having them for hundreds of years. In Old English, a mare was a kind of evil or cursed spirit. Mares appear in all kinds of folklore, including German and Slavic stories. Mares were said to ride on people's chests at night, causing suffocation and bad dreams. These mares, often female, were known as nightmares (because they came at night). By the 16th century, the word nightmare came to refer to a sensation of suffocation or anxiety during sleep, and now simply a bad dream. While nightmares are terrifying, there is good news: at least most of us don't worry about evil spirits trying to suffocate us in our sleep anymore. The roots of these other words may get a rise—of laughter or surprise—out of you. Run on over to our roundup of them at "Weird Word Origins That Will Make Your Family Laugh."
Related Words
See dream.
Other Word Forms
Etymology
Origin of nightmare
Middle English word dating back to 1250–1300; see origin at night, mare 2
Explanation
If you wake with a start after a terrifying dream, you've had a nightmare. A nightmare is not just a bad dream — it's seriously scary or upsetting. You can also use nightmare to describe something terrible that happens during the day. Your run-in with a skunk in your back yard might be a nightmare, for example, or your humiliating experience forgetting your lines in a play. In the late thirteenth century, a nightmare was "an evil female spirit afflicting sleepers with a feeling of suffocation," from the Old English word mare, "incubus or goblin."
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
A few of them were there on the last day at Dens Park in 1986 when a dream turned into their greatest nightmare.
From BBC • May 13, 2026
From afar, Chile's Tiltil landfill almost resembles just another mountain, but the growing rubbish pile has created a daily nightmare of odors, flies and health concerns for residents nearby.
From Barron's • May 13, 2026
This is when Maddin’s story switches from a survivalist nightmare to a legal one.
From Slate • May 13, 2026
While a jury ultimately cleared the singer of all charges in 2005, the experience is said to have left Jackson with very complex feelings about the home where the nightmare was said to have unfolded.
From MarketWatch • May 5, 2026
The idea that tens of thousands of people who labored, cooked meals, and ran households could rise up and leave—or worse—was a nightmare.
From "In the Shadow of Liberty" by Kenneth C. Davis
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
