nightmare🔊

(now rare) A demon or monster, thought to plague people while they slept and cause a feeling of suffocation and terror during sleep. +

(now chiefly historical) A feeling of extreme anxiety or suffocation experienced during sleep; Sleep paralysis.

A very bad or frightening dream.

(figuratively) Any bad, miserable, difficult or terrifying situation or experience that arouses anxiety, terror, agony or great displeasure.

To experience a nightmare.