INCUBUS, the name given in the middle ages to a male demon which was supposed to haunt women in their sleep, and to whose visits the birth of witches and demons was attributed. The word is a late Latin derivation (Augustine, Civ. Dei, Is. 23) of the classical incubare, to lie upon. The female counterparts of these demons, whose temptation of monks and other males bulked so large in the legends of the I I th and I 2th centuries, were known as succubae. In modern times the word has come to be generally used of an oppressive person or thing.