Source : Webster's Revised Unabridged Dictionary (1913)

Gallop \Gal"lop\, v. i. [imp. & p. p. {Galloped}; p. pr. & vb.
   n. {Galloping}.] [OE. galopen, F. galoper, of German origin;
   cf. assumed Goth. ga-hlaupan to run, OHG. giloufen, AS.
   gehle['a]pan to leap, dance, fr. root of E. leap, and a
   prefix; or cf. OFlem. walop a gallop. See {Leap}, and cf. 1st
   {Wallop}.]
   1. To move or run in the mode called a gallop; as a horse; to
      go at a gallop; to run or move with speed.

            But gallop lively down the western hill. --Donne.

Galloping \Gal"lop*ing\, a.
   Going at a gallop; progressing rapidly; as, a galloping
   horse.

Source : WordNet®

galloping
     adj : that are running rapidly; "surrounded by galloping horses"