Definitions
1.NounA defensive wall or rampart.
2.NounA defense or safeguard.
3.NounA breakwater.
4.NounThe planking or plating along the sides of a nautical vessel above her gunwale that reduces the likelihood of seas washing over the gunwales and people being washed overboard.
5.NounAny means of defence or security."The party stalwarts constitute the bulwark that ensures the president's term of office."
6.VerbTo fortify something with a wall or rampart.
7.VerbTo provide protection of defense for something.