PHAN'TASM, noun [Gr. to show, to shine, to appear.] That which appears to the mind; the image of an external object; hence, an idea or notion. It usually denotes a vain or airy appearance; something imagined. All the interim is Like a phantasm or a hideous dream.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI