synesthesia is an alternative spelling of synaesthesia.
The noun synaesthesia is defined as:
1. (neurology) A neurological or psychological phenomenon whereby a particular sensory stimulus triggers a second kind of sensation.
2. The association of one sensory perception with, or description of it in terms of, another, unlike, perception that is not experienced at the same time.
3. A literary or artistic device whereby one kind of sensation is described in the terms of another.
