Pronunciation: (nīt'mâr"), [key]
1. a terrifying dream in which the dreamer experiences feelings of helplessness, extreme anxiety, sorrow, etc.
2. a condition, thought, or experience suggestive of a nightmare: the nightmare of his years in prison.
3. (formerly) a monster or evil spirit believed to oppress persons during sleep.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.