bulwark
bul-wark
noun
A person or thing providing strong defence or support against harm or change.
"Free speech is a bulwark against tyranny."
noun
A defensive wall or structure, often part of a fortification or ship's side.
"The ancient bulwark protected the city from invaders."
Thesaurus
Synonyms: mole, breakwater, groyne, groin, jetty, seawall, wall, rampart