synaesthesia
From Longman Dictionary of Contemporary Englishsynaesthesiasyn‧aes‧the‧si‧a /ˌsɪnəsˈθiːziə $ -ʒə-/ noun [uncountable] a medical condition which makes people experience a mixture of feelings from two of their five senses at the same time, for example seeing numbers as colours or experiencing colours as a smell