*incubus*

n.; pl. E. Incubuses L. Incubi [ L., the nightmare. Cf. Incubate. ] [ 1913 Webster ]

1. A demon; a fiend; a lascivious spirit, supposed to have sexual intercourse with women by night. Tylor. [ 1913 Webster ]

The devils who appeared in the female form were generally called succubi; those who appeared like men incubi, though this distinction was not always preserved. Lecky. [ 1913 Webster ]

2. (Med.) The nightmare. See Nightmare. [ 1913 Webster ]

Such as are troubled with incubus, or witch-ridden, as we call it. Burton. [ 1913 Webster ]

3. Any oppressive encumbrance or burden; anything that prevents the free use of the faculties. [ 1913 Webster ]

Debt and usury is the incubus which weighs most heavily on the agricultural resources of Turkey. J. L. Farley. [ 1913 Webster ]