Definition of "crenellation" []

• A pattern along the top of a parapet (fortified wall), most often in the form of multiple, regular, rectangular spaces in the top of the wall, through which arrows or other weaponry may be shot, especially as used in medieval European architecture. (noun)
• The act of crenellating; adding a top row that looks like the top of a medieval castle. (noun)

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• "There is also mehrab, the niche where the Imam, or priest, leads the prayer and crenellation, which is the decoration on the top of the mosque."
• "A sparrow roosting in a bent crenellation took flight, but fell out of the sky."
• "They were quickly enlarged, vertically at first, and traces of the old crenellation are still visible in the second-story masonry."