The Collaborative International Dictionary of English v.0.48:

Dealer \Deal"er\, n.
   1. One who deals; one who has to do, or has concern, with
      others; esp., a trader, a trafficker, a shopkeeper, a
      broker, or a merchant; as, a dealer in dry goods; a dealer
      in stocks; a retail dealer.
      [1913 Webster]

   2. One who distributes cards to the players.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dealer
    n 1: someone who purchases and maintains an inventory of goods
         to be sold [syn: trader, bargainer, dealer, monger]
    2: a firm engaged in trading
    3: a seller of illicit goods; "a dealer in stolen goods"
    4: the major party to a financial transaction at a stock
       exchange; buys and sells for his own account [syn:
       principal, dealer]
    5: the person who distributes the playing cards in a card game

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "dealer":
   Mafioso, Wall Streeter, agent, black marketeer, bond crowd,
   bootlegger, broker, businessman, businesswoman, chandler,
   curb broker, distributor, drug pusher, floor broker, floor trader,
   floorman, gray marketeer, importer, jobber, marketer, merchandiser,
   merchant, middleman, monger, moonshiner, odd-lot dealer, pit man,
   pusher, racketeer, registered representative, regrater,
   retail dealer, retail merchant, retailer, salesman, sharebroker,
   shopkeeper, specialist, stock dealer, stock-exchange broker,
   stockbroker, stockjobber, storekeeper, supplier, trader, tradesman,
   tradeswoman, trafficker, two-dollar broker, vendor, wholesaler