bulwark
noun.
an embankment built around a space for defensive purposes
they stormed the ramparts of the city|they blew the trumpet and the walls came tumbling down
Synonym: rampart, wall
noun.
a fencelike structure around a deck (usually plural)
noun.
a protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away
verb.
defend with a bulwark