sleeper

Noun

• an unexpected hit
  • that movie was the sleeper of the summer
    

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

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

• pajamas with feet; worn by children

• a passenger car that has berths for sleeping

• one of the cross braces that support the rails on a railway track
  • the British call a railroad tie a sleeper
    

• an unexpected achiever of success
  • the winner was a true sleeper--no one expected him to get it
    

• 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

• a rester who is sleeping

Related words

• Synonyms: 
  sleeper goby , sleeping car , wagon-lit , tie , railroad tie , crosstie , slumberer