Entry 1 sense Webster, 1913 Summum bonum /sŭm'-əm bōn'-əm/ · Sum·mum bo·num · IPA /ˌsʊməm ˈbɑnəm/ 01 The supreme or highest good, -- referring to the object of human life. 1. The supreme or highest good, -- referring to the object of human life.(Philos.)