Definition from Wiktionary, the free dictionary
From the New Latin Prussia, a Latinization used by Peter of Dusburg of a Baltic-language autonym. The Middle English designation for the region, Pruce, derives from the same Latinization and is the source of the term spruce.
Proper noun 
- (chiefly historical) A geographical area on the Baltic coast of northeastern Europe.
- (historical) A Baltic country located in this area, conquered by the Teutonic Order and ultimately absorbed into Germany.
- (historical) A German province which was originally located in this area but later greatly expanded, and which was the predecessor to and a member of the German Empire; abolished as an administrative unit at the end of the Second World War.
Usage notes 
Related terms 
former baltic country