Source : Webster's Revised Unabridged Dictionary (1913)

Rolling \Roll"ing\, a.
   1. Rotating on an axis, or moving along a surface by
      rotation; turning over and over as if on an axis or a
      pivot; as, a rolling wheel or ball.

   2. Moving on wheels or rollers, or as if on wheels or
      rollers; as, a rolling chair.

   3. Having gradual, rounded undulations of surface; as, a
      rolling country; rolling land. [U.S.]

   {Rolling bridge}. See the Note under {Drawbridge}.

   {Rolling circle of a paddle wheel}, the circle described by
      the point whose velocity equals the velocity of the ship.
      --J. Bourne.

   {Rolling fire} (Mil.), a discharge of firearms by soldiers in
      line, in quick succession, and in the order in which they
      stand.

   {Rolling friction}, that resistance to motion experienced by
      one body rolling upon another which arises from the
      roughness or other quality of the surfaces in contact.

   {Rolling mill}, a mill furnished with heavy rolls, between
      which heated metal is passed, to form it into sheets,
      rails, etc.

   {Rolling press}.
      (a) A machine for calendering cloth by pressure between
          revolving rollers.
      (b) A printing press with a roller, used in copperplate
          printing.

   {Rolling stock}, or {Rolling plant}, the locomotives and
      vehicles of a railway.

   {Rolling tackle} (Naut.), tackle used to steady the yards
      when the ship rolls heavily. --R. H. Dana, Jr.

Source : WordNet®

rolling stock
     n : collection of wheeled vehicles owned by a railroad or motor
         carrier