Noun
(neurology, psychology) A neurological or psychological phenomenon whereby a particular sensory stimulus triggers a second kind of sensation. [from late 19th c.]
(by extension) The association of one sensory perception with, or description of it in terms of, a different perception that is not experienced at the same time.
(art, literature) A literary or artistic device whereby one kind of sensation is described in the terms of another.
Source: en.wiktionary.org