sleeper

Sense 1 noun

a rester who is sleeping

Sense 2 noun

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

Sense 3 noun

an unexpected achiever of success

the winner was a true sleeper--no one expected him to get it

Sense 4 noun

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

the British call a railroad tie a sleeper

Sense 5 noun

a passenger car that has berths for sleeping

Sense 6 noun

pajamas with feet; worn by children

Sense 7 noun

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

Sense 8 noun

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

Sense 9 noun

an unexpected hit

that movie was the sleeper of the summer