Incubus

Part of speech: noun (n.)

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

2. The nightmare. See Nightmare. Such as are troubled with incubus, or witch-ridden, as we call it. Burton.

3. Any oppressive encumbrance or burden; anything that prevents the free use of the faculties. Debt and usury is the incubus which weighs most heavily on the agricultural resources of Turkey. J. L. Farley.