1) Battlement 2) Bulwark 3) Crenellation 4) Rampart 5) Wall 1) Battlement 2) Crenellation 
• (n.) The act of crenelating, or the state of being crenelated; an indentation or an embrasure.
Battlements at the top of a tower or wall.
Battlements at the top of a tower or wall.
Cren`el·a'tion noun The act of crenelating, or the state of being crenelated; an indentation or an embrasure. [ Written also crenellation .]
Also called a battlement. This is a parapet (a low wall) constructed at the top of a larger wall for defensive purposes, behind which defenders can shelter or fight. It has alternating openings (crenels or embrasures) and raised sections (merlons).
[n] - the action of constructing rampparts with gaps for firing guns or arrows
crenellation noun the action of constructing ramparts with gaps for firing guns or arrows
a rampart built around the top of a castle with regular gaps for firing arrows or