Definition of "parapet"

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

2020 August 26, “Mid-September before line reopens, says Network Rail”, in Rail, page 11

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.

1907, Harold Bindloss, chapter 26, in The Dust of Conflict‎

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.

1938 April, George Orwell [pseudonym; Eric Arthur Blair], chapter I, in Homage to Catalonia, London: Secker & Warburg