Webster’s Revised Unabridged Dictionary · 1913 Succubus Suc′cu·bus (·bŭs), n.; pl. Succubi (#). [See Succuba.] 1. A demon or fiend; especially, a lascivious spirit supposed to have sexual intercourse with the men by night; a succuba. Cf. Incubus. 2. (Med.) The nightmare. See Nightmare, 2. ‹ Succubous Succula ›