An embrasure or indentation in a battlement; a loophole in a fortress; an indentation; a notch. See Merlon, and Illust. of Battlement.

one of a series of rounded projections (or the notches between them) formed by curves along an edge (as the edge of a leaf or piece of cloth or the margin of a shell or a shriveled red blood cell observed in a hypertonic solution etc.)

a notch or open space between two merlons in a crenelated battlement

Same as Crenature.