In'cu-būs, n.
n.; Eng. pl. IN'CU-BŪS-ES; Lat. pl. IN'CU-BI. [Lat., from incubare; It. & Sp. incubo, Fr. incube. See INCUBATE.]
Sense 1. A demon or fiend; an imaginary being or fairy. [Obs.] Bp. Hall.
Sense 2. (Med.) The nightmare; a sensation of a distressing weight at the chest or stomach during sleep, and of an impossibility of motion, speech, or respiration, from which one wakes in terror after extreme anxiety; hence, generally, any oppressive or stupefying influence. Dunglison.