Definition of "breakwater"

[…] there is a channel, some three miles wide between the city and the mainland, and some mile and a half wide between it and the sandy breakwater called the Lido, which divides the lagoon from the Adriatic,

1853, John Ruskin, “The Throne”, in The Stones of Venice, volume II (The Sea-Stories), London: Smith, Elder, and Co., […], § VI, page 8

But there's a pier or breakwater runs out into the sea just here, which we could defend longer than anything else, like Horatius and his bridge.

1908, G[ilbert] K[eith] Chesterton, The Man Who Was Thursday: A Nightmare, Bristol: J[ames] W[illiams] Arrowsmith, […]; London: Simpkin, Marshall, Hamilton, Kent & Company, page 259

They sailed around a breakwater that hadn't existed on Peregrine's last trip and tied in at the moorage.

1992, Vernor Vinge, A Fire Upon the Deep, New York: Tor Books, page 70