Definition of "sleeper"

Therefore let penal laws, if they have been sleepers of long, or if they be grown unfit for the present time, be by wise judged confined in the execution […]

1625, Francis [Bacon], “Of Judicature”, in The Essayes […], 3rd edition, London: […] Iohn Haviland for Hanna Barret

The object of these provisions is to prevent insertion of "jokers" or "sleepers" in bills and securing passage under the false color of the title.

1958, Duncan Leroy Kennedy, Bill drafting, page 12

I'll miss the sea. But a person needs new experiences. They draw something deep inside, allowing him to grow. Without change, something sleeps inside us and seldom awakens. The sleeper must awaken.

1984, 20:05 from the start, in Dune‎ (Science Fiction)

We are up against the pros; and pros who have been involved in this kind of activity for many years. […] The public apathy today is disturbing — few realize, Mr. Chairman, that there are sleepers in this country and we know that they are able to manipulate at will behind the scenes.

1969, United States Congress, Departments of Treasury and Post Office and Executive Office Appropriations for 1970: Hearings, (91st Congress, First Session, parts 2-3), page 479

It is realised that the old Pullman standard sleeper, with its convertible "sections", each containing upper and lower berths, and with no greater privacy at night than the curtains drawn along both sides of a middle aisle, has had its day.

1944 November and December, “"Duplex Roomette" Sleeping Cars”, in Railway Magazine, page 324

For example, the [racehorse] trainer may have tipped a betting syndicate that he is about to unleash a sleeper […]

1968, Marvin B. Scott, The Racing Game, page 160

At least a couple of weeks since I last slept, / Kept takin' sleepers, but now I keep myself pepped.

1995, “Insomnia”, in Reverence, performed by Faithless

I expect there ain't a trick to maverickin' and sleeperin' and changin' a brand he don't know.

1963, Jack Schaefer, Monte Walsh, page 81

The train, minus the three abandoned trucks, again proceeded at a slow pace, with a pump trolley doing pilot ahead ; this was very necessary as a great many sleepers were found to have been burnt underneath the fishplates.

1901, George Gipps, The Fighting in North China (up to the Fall of Tientsin City), Shanghai: Kelly and Walsh, page 40

I should imagine that the smooth riding and the quietness of the diesel or electric cab, coupled with the effect on the eyes of endless successions of sleepers disappearing from sight immediately under the driver's eyes, might in time have a soporific effect, so that the company of a second man, who can assist in signal observations when he is not at work in the engine cab, seems highly desirable in such conditions.

1961 July, Cecil J. Allen, “Locomotive Running Past and Present”, in Trains Illustrated, page 401