A very bad or frightening dream.
Any bad, miserable, difficult or terrifying situation or experience that arouses anxiety, terror, agony or great displeasure.
A feeling of extreme anxiety or suffocation experienced during sleep; Sleep paralysis.
To have a nightmare.
A threatening mental image.
Any of certain species of dragonfly of the genus Boyeria, family Aeshnidae.
A ghostly apparition, a phantom.