nightmare

A dream arousing feelings of intense fear, horror, and distress.

An event or experience that is intensely distressing.

A demon or spirit once thought to plague sleeping people.

An incubus or evil spirit that oppresses people during sleep.

An oppressed state during sleep, accompanied by a feeling of intense fear, horror, or anxiety, or of inability to escape from some threatened danger or from pursuing phantoms or monsters. Also called incubus.