Siberian UK /ˌsaɪˈbɪə.ɹi.ən/US /ˌsaɪˈbɪ.ɹi.ən/noun 2adjective 1forms 1 noun2 •A person from Siberia. •A long-haired domestic cat breed. adjective1 •Of or relating to Siberia. formsSiberians