Night-mare, a disease consisting in an oppression of the breast, so very violent, that the patient cannot speak or even breathe. The word is derived from the Latin incubare, to "lie down" on any thing and press it; the Greeks call it ἐπικάλυψις, q.d. fallator, "leaper," or one that rushes on a person.

In this disease the senses are not quite lost, but drowned, and astonished, as is the understanding and imagination; so that the patient seems to think some huge weight thrown on him, ready to strangle him. Children are very liable to this distemper; so are fat people, and men of much study and application of mind; by reason the stomach in all these finds some difficulty in digestion.