Source : Webster's Revised Unabridged Dictionary (1913)

Switching \Switch"ing\,
   a. & n. from {Switch}, v.

   {Switching engine}, a locomotive for switching cars from one
      track to another, and making up trains; -- called also
      {switch engine}. [U.S.]

Source : WordNet®

switch engine
     n : a locomotive for switching rolling stock in a railroad yard
         [syn: {donkey engine}]