The Collaborative International Dictionary of English v.0.48:
Incubus \In"cu*bus\, n.; pl. E. Incubuses, L. Incubi. [L.,
the nightmare. Cf. Incubate.]
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
2. (Med.) 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.