noun (n)

• a rester who is sleeping(noun.person)

  Synonym:
  slumberer
  

  source: wordnet30
• 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(noun.person)

  source: wordnet30
• an unexpected achiever of success(noun.person)

  Example:
  The winner was a true sleeper--no one expected him to get it.
  

  source: wordnet30
• one of the cross braces that support the rails on a railway track(noun.artifact)

  Example:
  The British call a railroad tie a sleeper.
  

  Synonym:
  crosstie, railroad tie, tie
  

  source: wordnet30
• a passenger car that has berths for sleeping(noun.artifact)

  Synonym:
  sleeping car, wagon-lit
  

  source: wordnet30
• pajamas with feet; worn by children(noun.artifact)

  source: wordnet30
• a piece of furniture that can be opened up into a bed(noun.artifact)

  source: wordnet30
• tropical fish that resembles a goby and rests quietly on the bottom in shallow water(noun.animal)

  Synonym:
  sleeper goby
  

  source: wordnet30
• an unexpected hit(noun.act)

  Example:
  That movie was the sleeper of the summer.
  

  source: wordnet30
• One who sleeps; a slumberer; hence, a drone, or lazy person.(noun)

  source: webster1913
• Something lying in a reclining posture or position.(noun)

  source: webster1913