The Collaborative International Dictionary of English v.0.48:

Doctor \Doc"tor\, v. t. [imp. & p. p. Doctored; p. pr. & vb.
   n. Doctoring.]
   1. To treat as a physician does; to apply remedies to; to
      repair; as, to doctor a sick man or a broken cart.
      [Colloq.]
      [1913 Webster]

   2. To confer a doctorate upon; to make a doctor.
      [1913 Webster]

   3. To tamper with and arrange for one's own purposes; to
      falsify; to adulterate; as, to doctor election returns; to
      doctor whisky. [Slang]
      [1913 Webster]