The Collaborative International Dictionary of English v.0.48:

Rowdy \Row"dy\, n.; pl. Rowdies. [From Rout, or Row a
   brawl.]
   One who engages in rows, or noisy quarrels; a ruffianly
   fellow. --M. Arnold.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rowdy
    adj 1: disturbing the public peace; loud and rough; "a raucous
           party"; "rowdy teenagers" [syn: raucous, rowdy]
    n 1: a cruel and brutal fellow [syn: bully, tough,
         hooligan, ruffian, roughneck, rowdy, yob, yobo,
         yobbo]

Moby Thesaurus II by Grady Ward, 1.0:

185 Moby Thesaurus words for "rowdy":
   Babbitt, Philistine, arriviste, bad, bad boy, battler, belligerent,
   belted knight, bickerer, blade, blaring, blatant, blatting,
   blustering, boisterous, booger, boor, boorish, bounder, bourgeois,
   brassy, bravo, brawler, brawling, brazen, bucko, buffoon, bugger,
   bully, bullyboy, cad, carlish, churl, churlish, clamant, clamorous,
   clamoursome, clanging, clangorous, clattery, cloddish, clown,
   clownish, combatant, competitor, contender, contestant, cutthroat,
   cutup, desperado, devil, disorderly, disputant, disruptive,
   duelist, elf, enfant terrible, enforcer, epicier, fencer, feuder,
   fighter, fighting cock, foilsman, funmaker, gamecock, gladiator,
   goon, gorilla, groundling, gunman, guttersnipe, harum-scarum,
   hatchet man, hell-raiser, hellcat, hood, hoodlum, hooligan,
   hooliganish, ill-bred fellow, imp, improper, joker, jokester,
   jouster, killer, knave, knight, knock-down-and-drag-out,
   knockabout, little devil, little monkey, little rascal, looby,
   loobyish, loud, lout, loutish, low fellow, lubberly, lumpish,
   mad dog, mafficking, militant, minx, misbehaving, mischief,
   mischief-maker, mucker, naughty, noiseful, noisy, not respectable,
   nouveau riche, obstreperous, off-base, out-of-line, parvenu,
   peasant, pixie, plug-ugly, practical joker, prankster, puck, punk,
   quarreler, rackety, raffish, rambunctious, rampageous, rapscallion,
   rascal, raucous, ribald, rioter, rip-roaring, rival, rogue,
   roisterous, rollicking, rough, rough-and-tumble, roughneck,
   rowdyish, ruffian, ruffianly, rumbustious, sabreur, scamp,
   scapegrace, scrapper, scuffler, skinhead, squabbler, strepitant,
   strepitous, strong arm, strong-arm man, strong-armer, struggler,
   swashbuckler, sword, swordplayer, swordsman, termagant, thug,
   tilter, tough, tumultuous, turbulent, tussler, unbehaving, unruly,
   uproarious, upstart, vociferous, vulgarian, vulgarist, wag, wild,
   wrangler, yahoo, yokel, yokelish