Main Entry: or·a·to·rio Pronunciation: "or-&-'tOr-E-"O, "är-, -'tor- Function: noun Inflected Form(s): plural -ri·os Etymology: Italian, from the Oratorio di San Filippo Neri (Oratory of Saint Philip Neri) in Rome Date: circa 1738 : a lengthy choral work usually of a religious nature consisting chiefly of recitatives, arias, and choruses without action or scenery