Alexander3Pronunciation: /ˌalɪgˈzɑːndə/Definition of Alexander the name of three tsars of Russia: Alexander I (1777–1825), reigned 1801–25. Alexander II (1818–81), son of Nicholas I, reigned 1855–81; known as Alexander the Liberator. His reforms included limited emancipation of the serfs. Alexander III (1845–94), son of Alexander II, reigned 1881–94. He reversed many of his father’s reforms, resulting in a dangerous situation in Russia. Alexander in other Oxford dictionaries Definition of Alexander in the US English dictionary