Source : Webster's Revised Unabridged Dictionary (1913)

Turntable \Turn"ta`ble\, n.
   A large revolving platform, for turning railroad cars,
   locomotives, etc., in a different direction; -- called also
   {turnplate}.

Source : WordNet®

turntable
     n 1: a circular horizontal platform that rotates a phonograph
          record while it is being played
     2: a revolving tray placed on a dining table [syn: {lazy Susan}]
     3: a rotatable platform with a track; used to turn locomotives
        and cars