Yenisei Syllabification: (Yen·i·sei)Pronunciation: /ˌyenəˈsā/ (also Yenisey)Definition of Yenisei a river in Siberia, in Russia, that rises in the mountains on the Mongolian border and flows north for 2,566 miles (4,106 km) to the Arctic coast, where it empties into the Kara Sea. Yenisei in other Oxford dictionaries Definition of Yenisei in the British & World English dictionary