Noun
1. a rester who is sleeping
2. 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
3. an unexpected achiever of success;
"the winner was a true sleeper--no one expected him to get it"4. one of the cross braces that support the rails on a railway track;
"the British call a railroad tie a sleeper"5. a passenger car that has berths for sleeping
6. a piece of furniture that can be opened up into a bed
7. tropical fish that resembles a goby and rests quietly on the bottom in shallow water
8. an unexpected hit;
"that movie was the sleeper of the summer"