Did you know?
Looking at nightmare, you might guess that it is a compound formed from night and mare. If so, your guess is correct. But while the night in nightmare makes sense, the mare part is less obvious. Most English speakers know mare as a word for a female horse or similar equine animal, but the mare of nightmare is a different word, an obsolete one referring to an evil spirit that was once thought to produce feelings of suffocation in people while they slept. By the 14th century the mare was also known as nightmare, and by the late 16th century nightmare was also being applied to the feelings of distress caused by the spirit, and then to frightening or unpleasant dreams.
Examples of nightmare in a Sentence
Zak Doffman, Forbes.com, 20 Apr. 2025
Eraserhead Year: 1977 Runtime: 1h 29m Director: David Lynch
One of the most polarizing filmmakers of all time made an impact from his debut film, this surreal nightmare that was released in arthouses back in 1977 and was an instant hit in major cities.
—Brian Tallerico, Vulture, 18 Apr. 2025
What begins as an ordinary parental milestone descends into a nightmare as a cross-border search unfolds.
—Nicholas Creel, MSNBC Newsweek, 18 Apr. 2025
And a deadly curse that turns their reality into a waking nightmare.
—Andreas Wiseman, Deadline, 17 Apr. 2025
See All Example Sentences for nightmare
Cite this Entry
“Nightmare.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/nightmare. Accessed 24 Apr. 2025.
Copy CitationKids Definition
nightmare
noun
Middle English nightmare "evil spirit thought to haunt people during sleep," from night "night" and mare "spirit," from Old English mare "evil spirit haunting people in sleep"
Medical Definition
nightmare
noun
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