antemural
/æntiˈmjʊərəl/Definitions
1. adjective
relating to or forming a defense or rampart in front of a wall or fortification
“The antemural bastion played a crucial role in the medieval castle’s defense system.”
2. noun
a defensive structure or wall in front of a fortification or other protected area
“The antemurals surrounding the ancient city provided an extra layer of protection.”