Bulwark

1. noun

   a protective structure of stone or concrete; extends from shore into the water to prevent a beach from washing away

   Similar: breakwater, groin, groyne, mole, seawall, jetty

2. noun

   an embankment built around a space for defensive purposes

   “they stormed the ramparts of the city”

   Similar: rampart, wall

3. noun

   a fencelike structure around a deck (usually plural)

4. verb

   defend with a bulwark