Phantasm

Part of speech: noun (n.)

1. An image formed by the mind, and supposed to be real or material; a shadowy or airy appearance; sometimes, an optical illusion; a phantom; a dream. They be but phantasms or apparitions. Sir W. Raleigh.

2. A mental image or representation of a real object; a fancy; a notion. Cudworth. Figures or little features, of which the description had produced in you no phantasm or expectation. Jer. Taylor.