castle

Noun

a large and stately mansion

Noun

a large building formerly occupied by a ruler and fortified against attack

Noun

(chess) the piece that can move any number of unoccupied squares in a direction parallel to the sides of the chessboard

Noun

interchanging the positions of the king and a rook

Verb

move the king two squares toward a rook and in the same move the rook to the square next past the king