Bad dream is a term used to describe a dream that is unpleasant or frightening. INCUBUS is a seven-letter term used to describe a male demon that visits people in their sleep and has sexual intercourse with them. SUCCUBUS is an eight-letter term used to describe a female demon that visits people in their sleep and has sexual intercourse with them. NIGHTMARE is a nine-letter term used to describe a very bad dream that causes feelings of fear, terror, and anxiety. NIGHTMARISH is an eleven-letter term used to describe something that is extremely frightening or horrible, like a NIGHTMARE.