n. 1. A dream arousing feelings of intense fear, horror, and distress. 2. An event or experience that is intensely distressing. 3. A demon or spirit once thought to plague sleeping people. [Middle English, a female demon that afflicts sleeping people : night, night; see NIGHT + mare, goblin (from Old English; see mer- in the Appendix of Indo-European roots).] nightmar′ish adj. nightmar′ish·ly adv. nightmar′ish·ness n. |
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