bulwark

(bo͝olˈwərk, -wôrkˌ, bŭlˈ-)

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. The part of a ship's side that is above the upper deck. Often used in the plural.

1. To fortify with a wall, embankment, or rampart.
2. To provide defense or protection for.