sleeper

noun

person who is sleeping
a piece of timber, stone, or steel on or near the ground to support a superstructure, keep railroad rails in place, or receive floor joists : stringpiece
someone or something unpromising or unnoticed that suddenly attains prominence or value
children's pajamas usually with feet —usually used in plural
sleeping car: a railroad passenger car having berths for sleeping

Pronunciation: /ˈsliːpə(ɹ)/

Etymology: Compare Norwegian sleip (“a sleeper (a timber); as adjective, slippery, smooth”). See slape.

A railroad tie.
“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.”
“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.”
A structural beam in a floor running perpendicular to both the joists beneath and floorboards above.
A heavy floor timber in a ship's bottom.
The lowest, or bottom, tier of casks.

Etymology: From Middle English sleper, equivalent to sleep + -er.

To mark a calf by cutting its ear.
“I expect there ain't a trick to maverickin' and sleeperin' and changin' a brand he don't know.”