The Collaborative International Dictionary of English v.0.48:

Trader \Trad"er\, n.
   1. One engaged in trade or commerce; one who makes a business
      of buying and selling or of barter; a merchant; a
      trafficker; as, a trader to the East Indies; a country
      trader.
      [1913 Webster]

   2. A vessel engaged in the coasting or foreign trade.
      [1913 Webster]

WordNet (r) 3.0 (2006):

trader
    n 1: someone who purchases and maintains an inventory of goods
         to be sold [syn: trader, bargainer, dealer, monger]