Castle (noun)

1. A large building or group of buildings fortified against attack with thick walls, battlements, towers, and in many cases a moat.
2. A large and imposing building, especially an official residence.
3. A type of chess piece.
4. A strategic defensive position or move in a game or sport.

Origin:

Middle english: from old french castel, from latin castellum, diminutive of castrum fort.

Examples:

1. The castle was built in the 13th century.
2. The castle was used as a royal residence for many centuries.
3. The knight is a castle piece in the game of chess.
4. The boxer took a castle position to avoid his opponent's punches.
5. The quarterback made a castle move to protect the ball.