[night.mare] n [ME, fr. [1]night + [1]mare] (14c) 1: an evil spirit formerly thought to oppress people during sleep
2: a frightening dream that usu. awakens the sleeper
3: something (as an experience, situation, or object) having the monstrous character of a nightmare or producing a feeling of anxiety or terror -- nightmare adj -- night.mar.ish adj -- night.mar.ish.ly adv