'sleeper' in a sentence

: a rester who is sleeping

: 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

: an unexpected achiever of success

: one of the cross braces that support the rails on a railway track

: a passenger car that has berths for sleeping

: pajamas with feet; worn by children

: a piece of furniture that can be opened up into a bed

: tropical fish that resembles a goby and rests quietly on the bottom in shallow water

: an unexpected hit