Spectrum, spectri, n. g. Ci. An image or figure in a mans imagination: a ghost.
Lewis and Short: Latin dictionary
spectrum, i, n. [specio], an appearance, form, image of a thing; an apparition, spectre, the Gr. ei)/dwlon (much less freq. than simulacrum and species): spectra Catiana ... nam quae Democritus ei)/dwla, Catius Insuber Epicureus spectra nominat, Cic. Fam. 15, 16, 1 sq.: spectra Catiana, Cass. ap. Cic. Fam. 15, 19, 1.