Belorussia

(bĕlˌō-rŭshˈə, byĕlˌ-) or Bye·lo·rus·sia (byĕlˌō-) Popularly known as White Russia 

1. A region of eastern Europe in present-day Belarus and Poland. Settled by Slavs in the 5th century, it became a part of the grand duchy of Lithuania in the 14th century, merged with Poland in 1569, and was annexed by Russia in the 18th century. In 1921 the western part of the region was ceded to Poland, and the eastern part became the Belorussian Soviet Socialist Republic, now Belarus.
2. See Belarus.