Mackintosh, Charles Rennie Syllabification: (Mack·in·tosh, Charles Rennie)Pronunciation: /ˈmakənˌtäSH/Definition of Mackintosh, Charles Rennie (1868–1928), Scottish architect, designer, and painter. A leading exponent of art nouveau, he pioneered the new concept of functionalism in architecture and interior design. Mackintosh, Charles Rennie in other Oxford dictionaries Definition of Mackintosh, Charles Rennie in the British & World English dictionary