Main Entry: night·mare

Pronunciation: \ˈnīt-ˌmer\

Function: noun

Etymology: Middle English, from ¹night + ¹mare

Date: 14th century

1 : an evil spirit formerly thought to oppress people during sleep
2 : a frightening dream that usually 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 adjective

— night·mar·ish \-ˌmer-ish\ adjective

— night·mar·ish·ly adverb