- a terrifying or deeply distressing dream
- an event or condition resembling a terrifying dream
- (as modifier): a nightmare drive
- a thing that is feared
- (formerly) an evil spirit supposed to harass or suffocate sleeping people
WordReference Random House Learner's Dictionary of American English © 2026
night•mare /ˈnaɪtˌmɛr/USA pronunciation
n. [countable]
WordReference Random House Unabridged Dictionary of American English © 2026- a frightening or terrifying dream that produces feelings of great fear and anxiety.
- a condition, thought, or experience that is very unpleasant:Driving through that city at rush hour is a nightmare.
night•mare
(nīt′mâr′),USA pronunciation n.
- a terrifying dream in which the dreamer experiences feelings of helplessness, extreme anxiety, sorrow, etc.
- a condition, thought, or experience suggestive of a nightmare:the nightmare of his years in prison.
- Mythology(formerly) a monster or evil spirit believed to oppress persons during sleep.
- 1250–1300; Middle English; see night, mare2
- 1. . phantasmagoria. See dream.
Collins Concise English Dictionary © HarperCollins Publishers::
nightmare /ˈnaɪtˌmɛə/ n
'nightmare' also found in these entries (note: many are not synonyms or translations):
Fuseli
- incubus
- Peacock
- dream
- elfin
- fantasy
- mare
- nightmarish
- night terror
- oaf
- phantasmal