The Collaborative International Dictionary of English v.0.48:

March \March\, v. i. [imp. & p. p. Marched; p. pr. & vb. n.
   Marching.] [F. marcher, in OF. also, to tread, prob. fr. L.
   marcus hammer. Cf. Mortar.]
   1. To move with regular steps, as a soldier; to walk in a
      grave, deliberate, or stately manner; to advance steadily.
      --Shak.
      [1913 Webster]

   2. To proceed by walking in a body or in military order; as,
      the German army marched into France.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Marching \March"ing\,
   a. & n., fr. March, v.
   [1913 Webster]

   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.
       [1913 Webster]

WordNet (r) 3.0 (2006):

marching
    n 1: the act of marching; walking with regular steps (especially
         in a procession of some kind); "it was a long march"; "we
         heard the sound of marching" [syn: march, marching]

Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "marching":
   ambling, ambulation, backpacking, footing, footing it, footwork,
   going on foot, hiking, hitchhiking, hitching, hoofing, legwork,
   lumbering, pedestrianism, perambulation, sauntering, staggering,
   strolling, thumbing, thumbing a ride, toddling, tottering,
   tramping, treading, trudging, waddling, walking