1. A large building formerly occupied by a ruler and fortified against attack
   "Tourists flocked to see the medieval castle perched atop the hill"
    
2. A large and stately mansion
   "The ancient castle loomed over the countryside, a testament to medieval architecture";
   - palace
    
3. (chess) the piece that can move any number of unoccupied squares in a direction parallel to the sides of the chessboard
   "She moved her castle";
   - rook
    
4. Interchanging the positions of the king and a rook
   "Her timely castle protected the king from the opponent's attack";
   - castling

1. (chess) move the king two squares toward a rook and in the same move the rook to the square next past the king
   "He castled early in the game to protect his king"

Derived forms: castling, castled, castles

Type of: chess move, chess piece, chessman, fortification [rare], go, hall, manse [archaic], mansion, mansion house, move, munition, residence

Encyclopedia: Castle, Newcastle upon Tyne