Definition of "turnkey"

Third World countries no longer want to purchase nuclear projects on a turn-key basis; they want to receive advanced technical training as well.

1980, Bulletin of the Atomic Scientists, April 1980, Kathleen Bailey, When and why weapons; page 42

He cautioned that the house “is not turnkey,” and that because it is “so unusual,” it may take a while to sell. But, he added, “It’s a joy to be selling a property with its history.”

2023 March 22, Ben West, “This 835-Year-Old English Manor Needs Some Modern Love”, in The New York Times‎

He saw the same Turnkey unfetter a man / With but little expedition, / Which put him in mind of the long debate / On the Slave-trade abolition.

1834 , Samuel Taylor Coleridge, Robert Southey, “The Devil's Thoughts”, in The Poetical Works of S. T. Coleridge, volume II, London: W. Pickering, page 86

[…] they passed through an open door into a lobby, from which a heavy gate, opposite to that by which they had entered, and which was guarded by a stout turnkey with the key in his hand, led at once into the interior of the prison.

1836 March – 1837 October, Charles Dickens, “(please specify the chapter name)”, in The Posthumous Papers of the Pickwick Club, London: Chapman and Hall, […], published 1837

'Certainly not,' said the turnkey; and the first corroborated his statement.

1883, Thomas Hardy, The Three Strangers‎