Of or relating to the East Slavs, their culture or language(s).

A subgrouping of the Slavic language family spoken mainly in Belarus, Russia and Ukraine. / (historical, rare) The Old East Slavic language.

(historical) A Slavic language used from the 10th to the 14th centuries by East Slavs in the state of Kievan Rus and its successors. The ancestor of Belarusian, Russian, Rusyn and Ukrainian.