Possible Definitions:
1. Castle (n.) A fortified residence, especially that of a prince or nobleman; a fortress.
2. Castle (n.) Any strong, imposing, and stately mansion.
3. Castle (n.) A small tower, as on a ship, or an elephant's back.
4. Castle (n.) A piece, made to represent a castle, used in the game of chess; a rook.
5. Castle (v. i.) To move the castle to the square next to king, and then the king around the castle to the square next beyond it, for the purpose of covering the king.
