The Collaborative International Dictionary of English v.0.48:

Turntable \Turn"ta`ble\, n.
   A large revolving platform, for turning railroad cars,
   locomotives, etc., in a different direction; -- called also
   turnplate.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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: turntable,
       lazy Susan]
    3: a rotatable platform with a track; used to turn locomotives
       and cars