Schloss (pl. Schlösser) is a German word for a building similar to a Château, castle, palace, or manor house; what in the British Isles would be known as a stately home. Most Schlösser were built after the Middle Ages as residences or for organizational headquarters and not as fortresses.
Like castles, a Schloss is often surrounded by moats and is called a Wasserschloss (water castle). Other types include the Jagdschloss (hunting lodge) and the Lustschloss (pleasure castle).
Note in another context Schloss is also German for a lock.