Meaning : A large building formerly occupied by a ruler and fortified against attack.
Meaning : (chess) the piece that can move any number of unoccupied squares in a direction parallel to the sides of the chessboard.
Synonyms : rook
Meaning : Interchanging the positions of the king and a rook.
Synonyms : castling
Meaning : Move the king two squares toward a rook and in the same move the rook to the square next past the king.