a spy or saboteur or terrorist planted in an enemy country who lives there as a law-abiding citizen until activated by a prearranged signal
"The intelligence agency believed the quiet accountant was actually a sleeper waiting for orders to strike."
an unexpected achiever of success
"the winner was a true sleeper--no one expected him to get it"
one of the cross braces that support the rails on a railway track
"the British call a railroad tie a sleeper"
a passenger car that has berths for sleeping
"After a long day of driving, we pulled into the rest stop to spend the night in our sleeper before continuing our cross-country trip."
pajamas with feet; worn by children
"After taking off his regular sleepers, little Timmy curled up in bed to dream about dinosaurs."
a piece of furniture that can be opened up into a bed
"After the party, I pulled out the sleeper in the living room to let my tired guests crash on it."
tropical fish that resembles a goby and rests quietly on the bottom in shallow water
"The angler carefully lowered his net into the murky shallows to catch the elusive sleeper hiding among the sand."
Someone who sleeps.
"The old freight train was held up because a broken sleeper had shifted out of place on the tracks."
A railroad tie.
To mark a calf by cutting its ear.
"The rancher used a sharp knife to sleeper the new calves before branding them for identification."
A surname.
"The Sleeper family has lived on that farm for three generations."