bul·wark 
(blwərk, -wôrk′, bŭl-)
(blwərk, -wôrk′, bŭl-)n.
1. A wall or embankment raised as a defensive fortification; a rampart.
2. Something serving as a defense or safeguard: "We have seen the necessity of the Union, as our bulwark against foreign danger" (James Madison).
3. A breakwater.
4. often bulwarks The part of a ship's side that is above the upper deck.
tr.v. bul·warked, bul·wark·ing, bul·warks
1. To fortify with a wall, embankment, or rampart.
2. To provide defense or protection for: "the wetland that bulwarked the pond" (Edward Hoagland).
[Middle English bulwerk, from Middle Dutch bolwerk, from Middle High German bolwerc : bole, plank; see bhel-2 in the Appendix of Indo-European roots + werc, work (from Old High German; see werg- in the Appendix of Indo-European roots).]
Synonyms: bulwark, barricade, breastwork, earthwork, rampart, bastion, parapet
These nouns refer literally to structures used as a defense against attack. A bulwark is a strong defensive barrier, often an embankment or wall-like fortification, from which fire can be directed. A barricade is an improvised barrier meant to stop or slow an advancing threat. Breastwork denotes a low defensive wall, especially a temporary one hurriedly built. An earthwork is an embankment made of soil, and may include a trench or moat. A rampart, the main defensive structure around a guarded place, is permanent, high, and broad. A bastion is a projecting section of a fortification from which defenders have a wide range of view and fire. Parapet applies to any low fortification, typically a wall atop a rampart. Of these words bulwark, bastion, and rampart are the most frequently used to refer figuratively to something regarded as being a safeguard or a source of protection: "The only sure bulwark of continuing liberty is a government strong enough to protect the interests of the people, and a people strong enough ... to maintain its sovereign control over its government" (Franklin D. Roosevelt). "the University of Virginia, a school founded by Jefferson to be a bastion of free thought" (Garry Wills). "The sense of being a couple ... is the strongest rampart against the relentless threat of our divorce culture" (Judith S. Wallerstein).
These nouns refer literally to structures used as a defense against attack. A bulwark is a strong defensive barrier, often an embankment or wall-like fortification, from which fire can be directed. A barricade is an improvised barrier meant to stop or slow an advancing threat. Breastwork denotes a low defensive wall, especially a temporary one hurriedly built. An earthwork is an embankment made of soil, and may include a trench or moat. A rampart, the main defensive structure around a guarded place, is permanent, high, and broad. A bastion is a projecting section of a fortification from which defenders have a wide range of view and fire. Parapet applies to any low fortification, typically a wall atop a rampart. Of these words bulwark, bastion, and rampart are the most frequently used to refer figuratively to something regarded as being a safeguard or a source of protection: "The only sure bulwark of continuing liberty is a government strong enough to protect the interests of the people, and a people strong enough ... to maintain its sovereign control over its government" (Franklin D. Roosevelt). "the University of Virginia, a school founded by Jefferson to be a bastion of free thought" (Garry Wills). "The sense of being a couple ... is the strongest rampart against the relentless threat of our divorce culture" (Judith S. Wallerstein).