The Collaborative International Dictionary
Photism \Pho"tism\, n. [Gr. ? illumination.] (Psycol.) A luminous image or appearance of a hallucinatory character.
n. 1 (context psychology English) A luminous appearance, image or subjective perception of a hallucinatory nature. 2 The color that a synesthete may report seeing in association with a particular letter or number.
Usage examples of "photism".
I was to learn later that he was subject to certain photisms, or optical hallucinations, as well, but fortunately was spared that extra cause for alarm during this first experience of vehicular traffic).