Proper noun
Peipus
A large freshwater lake on the border between Estonia and Russia in Northern Europe. It is the fifth-largest lake in Europe, and the largest in Estonia. The lake consists of three parts: Peipsi (Chudskoe), Pihkva (Pskovskoe), Lämmijärv (Teploe).
The largest of them, Lake Peipus (convert), forms much of the border between Estonia and Russia. Source: Internet