The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

            But gallop lively down the western hill. --Donne.
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   2. To ride a horse at a gallop.
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   3. Fig.: To go rapidly or carelessly, as in making a hasty
      examination.
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            Such superficial ideas he may collect in galloping
            over it.                              --Locke.
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The Collaborative International Dictionary of English v.0.48:

Gallop \Gal"lop\, v. t.
   To cause to gallop.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gallop \Gal"lop\, n. [Cf. F. galop. See Gallop, v. i., and cf.
   Galop.]
   A mode of running by a quadruped, particularly by a horse, by
   lifting alternately the fore feet and the hind feet, in
   successive leaps or bounds.
   [1913 Webster]

   Hand gallop, a slow or gentle gallop.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gallop
    n 1: a fast gait of a horse; a two-beat stride during which all
         four legs are off the ground simultaneously
    v 1: ride at a galloping pace; "He was galloping down the road"
    2: go at galloping speed; "The horse was galloping along"
    3: cause to move at full gallop; "Did you gallop the horse just
       now?" [syn: gallop, extend]

Moby Thesaurus II by Grady Ward, 1.0:

98 Moby Thesaurus words for "gallop":
   amble, bound, burst, burst of speed, canter, caracole, curvet,
   dash, dead run, dogtrot, drag, droop, flank speed, flat-out speed,
   flounce, forced draft, fox-trot, frisk, full gallop, gait, get,
   git, go on horseback, hack, hand gallop, headlong rush,
   heavy right foot, high lope, hightail, hitch, hobble, hop,
   hop along, hotfoot, jog, jog trot, leap, limp, lock step, lope,
   lurch, make tracks, maximum speed, mince, mincing steps, mount,
   open throttle, pace, paddle, piaffe, piaffer, plunge, prance, race,
   rack, ride bareback, ride hard, roll, run, rush, saunter, scamper,
   scud, scurry, scuttle, shamble, shuffle, sidle, single-foot, slink,
   slither, slouch, slowness, spring, sprint, spurt, stagger, stalk,
   step, step along, step lively, stride, stroll, strolling gait,
   strut, swagger, swing, take horse, tittup, toddle, totter, tread,
   trip, trot, velocity, waddle, walk, wide-open speed