or ‧ a ‧ to ‧ ri ‧ o /ˌɒrəˈtɔːriəʊ $ ˌɔːrəˈtɔːrioʊ, ˌɑː-/ BrE AmE noun ( plural oratorios ) [countable]
[ Date: 1600-1700 ; Language: Italian ; Origin: from the Oratorio di San Filippo Neri, church in Rome where such music was first performed ]
a long piece of music in which a large group of people sing