Entry 1 sense Webster, 1913 Mackintosh /măk'-ən-täshˌ/ · Mack·in·tosh · IPA /ˈmækɪntɑʃ/ 01 n. A waterproof outer garment; -- so called from the name of the inventor. 1. A waterproof outer garment; -- so called from the name of the inventor.