Definition of "sewer"

One of the hidden glories of Victorian engineering is proper drains. Isolating a city’s effluent and shipping it away in underground sewers has probably saved more lives than any medical procedure except vaccination.

2014 June 14, “It's a gas”, in The Economist‎, volume 411, number 8891

While the Saxon was plunged in these painful reflections, the door of their prison opened, and gave entrance to a sewer, holding his white rod of office.

1819, Walter Scott, Ivanhoe

His nephew Charles, meanwhile, had grown up in the royal household, working as a sewer, or waiter.

2011, Thomas Penn, Winter King, Penguin, published 2012, page 287

Up under the roof three men are making boys’ jackets at twenty cents a piece, of which the sewer takes eight, the ironer three, the finisher five cents, and the buttonhole-maker two and a quarter, leaving a cent and three-quarters to pay for the drumming up, the fetching and bringing back of the goods.

1890, Jacob A[ugust] Riis, “The Sweaters of Jewtown”, in How the Other Half Lives: Studies among the Tenements of New York, New York, N.Y.: Charles Scribner’s Sons, pages 131–132