1. [N. Amer] A piece of furniture that can be opened up into a bed
   "The guests slept comfortably on the sleeper sofa in the living room"
    
2. A passenger car that has berths for sleeping
   "They booked a compartment in the sleeper for their overnight train journey";
   - sleeping car, wagon-lit
    
3. [Brit] One of the cross braces that support the rails on a railway track
   "the British call a railway crosstie a sleeper";
   - tie [N. Amer], railroad tie [N. Amer], crosstie [N. Amer]
    
4. Someone who is sleeping
   "The peaceful sleeper didn't hear the alarm clock";
   - slumberer
    
5. An unexpected achiever of success
   "the winner was a true sleeper — no one expected him to get it"
    
6. An unexpected hit
   "that movie was the sleeper of the summer"
    
7. A spy, saboteur or terrorist planted in an enemy country who lives there as a law-abiding citizen until activated by a prearranged signal
   "The sleeper had been living in the country for years before receiving orders to act"
    
8. [N. Amer] Pyjamas with feet; worn by children
   "The toddler wore a cosy fleece sleeper to bed"
    
9. Tropical fish that resembles a goby and rests quietly on the bottom in shallow water
   "The sleeper goby's camouflage allows it to blend in with the seafloor";
   - sleeper goby
    
10. A structural beam in a floor
    "The carpenter replaced the rotten sleeper to stabilize the floor"

Derived forms: sleepers

Type of: achiever, article of furniture, bang [informal], brace, bracing, carriage, coach, diversionist, furniture, hit, jammies [N. Amer, informal], jim-jams [Brit, informal], pajama, passenger car, percoid, percoid fish, percoidean, piece of furniture, pj's [informal], pyjama, rester, saboteur, sizzler [informal], smash, smasher [informal], spy, strike, succeeder, success, terrorist, undercover agent, winner, wrecker

Part of: Eleotridae, family Eleotridae, railroad [N. Amer], railroad track [N. Amer], railway [Brit, Cdn], railway track [Brit, Cdn], sleeper nest

Encyclopedia: Sleeper, Thomas