Definition of "fluke"

“ […] That's the first time in the history of Bierce's Cove that two men made that jump on the same sea. And all the risk was yours, coming last.”“It was a fluke,” Billy insisted.

1913 October, Jack London, chapter VIII, in The Valley of the Moon, New York, N.Y.: The Macmillan Company

Three of the best hitters in the Eastern retired on nine strikes! That was no fluke.

1920, Zane Grey, “The Rube”, in The Redheaded Outfield‎

"And I say," said Wimsey, "that it would be better for her to be hanged outright than to live and have everybody think her a murderess who got off by a fluke."

1930, Dorothy L. Sayers, Strong Poison

It's Christmas at ground zero / Now the missiles are on their way / What a crazy fluke / We're gonna get nuked / On this jolly holiday

1986, "Weird Al" Yankovic (lyrics and music), “Christmas at Ground Zero”, in Polka Party!‎

And before I forget... that was one amazing kiss, mister. Could have been a fluke, though. Guess we have to keep trying.

2017, BioWare, Mass Effect: Andromeda (Science Fiction), Redwood City: Electronic Arts, PC, scene: Garden

That this was not just a fluke was proved by a further profit the following year, albeit cut due to industrial action - jam at last!

2020 January 2, David Clough, “How InterCity came back from the brink”, in Rail, page 69

But though this sculpture is half man and half whale, so as only to give the tail of the latter, yet that small section of him is all wrong. It looks more like the tapering tail of an anaconda, than the broad palms of the true whale's majestic flukes.

1851 November 14, Herman Melville, chapter 55, in Moby-Dick; or, The Whale, 1st American edition, New York, N.Y.: Harper & Brothers; London: Richard Bentley

As Walter de la Mare writes, "How uncomprehendingly must an angel from heaven smile on a poor human sitting engrossed in a romance: angled upon his hams, motionless in his chair, spectacles on nose, his two feet as close together as the flukes of a merman's tail, only his strange eyes stirring in his time-worn face."

1919, Christopher Morley, chapter IX, in The Haunted Bookshop‎, New York, N.Y.: Grosset & Dunlap Publishers

The honest, rough piece of iron, so simple in appearance, has more parts than the human body has limbs: the ring, the stock, the crown, the flukes, the palms, the shank. All this, according to the journalist, is “cast” when a ship arriving at an anchorage is brought up.

1904–1906, Joseph Conrad, chapter IV, in The Mirror of the Sea, 1st American edition, New York, N.Y., London: Harper & Brothers, published October 1906