Proto-Indo-European UK /ˌpɹəʊ̯təʊ̯ˌɪndə(ʊ̯)ˌjʊə̯ɹəˈpiːən/US /ˌpɹoʊ̯toʊ̯ˌɪndoʊ̯ˌjʊɹəˈpi.ən/adjective 1noun 1forms 1 adjective1 •Of or pertaining to the Proto-Indo-European language, or the people who spoke it. noun1 •A person who spoke the Proto-Indo-European language. formsProto-Indo-Europeans