A fortress is a castle or other large strong building, or a well-protected place, which is intended to be difficult for enemies to enter. a 13th-century fortress. a large strong building used for defending an important place (forteresse , from fortis )
[ 'for-tr&s ] (noun.) 14th century. Middle English forteresse, from Middle French forteresce, from Medieval Latin fortalitia, from Latin fortis strong.