Semei Syllabification: (Se·mei)Pronunciation: /ˈsemā/ (also Semey)Definition of Semei an industrial city and river port in eastern Kazakhstan, on the Irtysh River, close to the border with Russia; population 281,800 (est. 2006). Founded in the 18th century, it was known as Semipalatinsk until 1991. Semei in other Oxford dictionaries Definition of Semei in the British & World English dictionary