Sentence:  The main walls were carried to the top of the fourth story, where a capacious <WSD>machicolation</WSD> enclosed the tower, on which there is a parapet wall of great thickness, with arches: this was to protect the persons employed over the <WSD>machicolations</WSD>. 
Meaning of the word marked with <WSD> tags:  A projecting parapet with a series of such openings.