Definition of nightmare noun from the Oxford Advanced Learner's Dictionary. a dream that is very frightening or unpleasant. He still has nightmares about the accident. She has a recurring nightmare about being stuck in a lift. Survivors suffer flashbacks, nightmares and severe depression. : something (such as an experience, situation, or object) having the monstrous character of a nightmare or producing a feeling of anxiety or terror. Did you know? Looking at nightmare, you might guess that it is a compound formed from night and mare. If so, your guess is correct. Nightmares are more than just unsettling experiences that disrupt your sleep; they can also offer valuable insights into your mental and emotional state. Research shows that nightmares are a normal part of the dreaming process and can reflect various aspects of our waking lives. Understanding the nightmare meanings can help you recognize underlying issues, manage stress, and find ways to improve your well-being. Today, we’ll explore some of the most nightmares and their meanings, shedding ... A nightmare is a very upsetting or frightening dream, or an extremely unpleasant event or experience. Learn more about the meaning, usage and origin of this word with Cambridge Dictionary.