The title of the emperor of Russia. See Czar.

Slavic equivalent of the Greek basileus, emperor. The Slavs used it for the Byzantine emperor, and in time when Slavic rulers - i.e., the rulers of the Second Bulgarian Empire and Dusan of Serbia - claimed for themselves the imperial title, they called themselves tsars. (Fine, John V.A. Jr. The Late Medieval Balkans, 627)

a male monarch or emperor (especially of Russia prior to 1917)

Slavic equivalent for the Greek term "Basileus," which was used for the Byzantine Emperor. Later, when the rulers of Bulgaria's Second Empire, Dušan of Serbia and eventually when Russia's Ivan IV claim the imperial title for themselves, they utilize the term "Tsar."

in Russia and certain other Slavic countries, a male monarch.

Tsar (Bulgarian, Serbian and Macedonian цар, Russian , in scientific transliteration respectively car and car' ), occasionally spelled Czar or Tzar and sometimes Csar or Zar in English, is a Slavonic term designating certain monarchs.