The Collaborative International Dictionary of English v.0.48:

Flog \Flog\ (fl[o^]g), v. t. [imp. & p. p. Flogged (fl[o^]gd);
   p. pr. & vb. n. Flogging (-g[i^]ng).] [Cf. Scot. fleg blow,
   stroke, kick, AS. flocan to strike, or perh. fr. L.
   flagellare to whip. Cf. Flagellate.]
   To beat or strike with a rod or whip; to whip; to lash; to
   chastise with repeated blows.
   [1913 Webster]

WordNet (r) 3.0 (2006):

flog
    v 1: beat severely with a whip or rod; "The teacher often
         flogged the students"; "The children were severely
         trounced" [syn: flog, welt, whip, lather, lash,
         slash, strap, trounce]
    2: beat with a cane [syn: cane, flog, lambaste, lambast]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "flog":
   baste, bastinado, beat, belabor, belt, birch, buffet, cane,
   castigate, chastise, club, cowhide, cudgel, cut, drub, flagellate,
   flail, flay, fustigate, give a whipping, give the stick, goad,
   hide, horsewhip, knout, lace, larrup, lash, lather, lay on, needle,
   nudge, pistol-whip, poke, pommel, prick, prod, promote, publicize,
   pummel, punish, rawhide, scourge, sell, smite, spank, spur, sting,
   strap, stripe, swinge, switch, thrash, thresh, thump, trounce,
   truncheon, wallop, whale, whip, whop