The north-eastern part of the former kingdom of Prussia, on the Baltic coast, later part of Germany and divided after the Second World War between the Soviet Union and Poland.
东普鲁士（原普鲁士王国东北部地区，位于波罗的海沿岸，后为德国一地区，二战后分属苏联和波兰）
Definition of East Prussia in US English:
East Prussia
proper noun
The northeastern part of the former kingdom of Prussia, on the Baltic coast, later part of Germany and divided after World War II between the former Soviet Union and Poland.