parapet

noun

1. A low protective wall.

   “Engineers will be closely checking the bridge for damage beyond the obvious smashed parapets.”

2. Part of a perimeter that extends above the roof.

   “Maccario, it was evident, did not care to take the risk of blundering upon a picket, and a man led them by twisting paths until at last the hacienda rose blackly before them. Appleby could see it dimly, a blur of shadowy buildings with the ridge of roof parapet alone cutting hard and sharp against the clearing sky.”

3. A fortification consisting of a wall.

   “Obviously if you have only a few days in which to train a soldier, you must teach him the things he will most need; how to take cover, how to advance across open ground, how to mount guards and build a parapet – above all, how to use his weapons.”