- 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.
- (formerly) a monster or evil spirit believed to oppress persons during sleep.
- a terrifying or deeply distressing dream
- an event or condition resembling a terrifying dream
- (as modifier)
- a thing that is feared
- (formerly) an evil spirit supposed to harass or suffocate sleeping people
