Pronunciation: (in'kyu-bus, ing'-),[key] —n., —pl.-biPronunciation: (-bī"),[key]-bus•es. 1. an imaginary demon or evil spirit supposed to descend upon sleeping persons, esp. one fabled to have sexual intercourse with women during their sleep. Cf. succubus (def. 1).
2. a nightmare.
3. something that weighs upon or oppresses one like a nightmare.