Source : Webster's Revised Unabridged Dictionary (1913)

Marching \March"ing\,
   a. & n., fr. {March}, v.

   {Marching money} (Mil.), the additional pay of officer or
      soldier when his regiment is marching.

   {In marching order} (Mil.), equipped for a march.

   {Marching regiment}. (Mil.)
   (a) A regiment in active service.
   (b) In England, a regiment liable to be ordered into other
       quarters, at home or abroad; a regiment of the line.