crenelation

from The Century Dictionary.

• noun The act of rendering a building defensible by the addition of battlements or by the cutting of loopholes. See crenelate, v.
• noun The state or condition of being crenelated.
• noun A battlement.
• noun Any notch or indentation.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of crenelating, or the state of being crenelated; an indentation or an embrasure.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Alternative form of crenellation.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the action of constructing ramparts with gaps for firing guns or arrows
• noun a rampart built around the top of a castle with regular gaps for firing arrows or guns