1.  crenelation(n = noun.artifact) battlement, crenellation - a rampart built around the top of a castle with regular gaps for firing arrows or guns;
is a kind of bulwark, rampart, wall
is a part of fort, fortress
has parts: crenel, crenelle, merlon
Derived form verb crenelate₁

2.  crenelation(n = noun.act) crenellation - the action of constructing ramparts with gaps for firing guns or arrows;
is a kind of building, construction
Derived form verb crenelate₁

   The act of crenelating, or the state of being crenelated; an indentation or an embrasure. [1913 Webster]