The Collaborative International Dictionary of English v.0.48:

Mercantile \Mer"can*tile\ (?; 277), a. [F. mercantile, It.
   mercantile, fr. L. mercans, -antis, p. pr. of mercari to
   traffic. See Merchant.]
   Of or pertaining to merchants, or the business of merchants;
   having to do with trade, or the buying and selling of
   commodities; commercial.
   [1913 Webster]

         The expedition of the Argonauts was partly mercantile,
         partly military.                         --Arbuthnot.
   [1913 Webster]

   Mercantile agency, an agency for procuring information of
      the standing and credit of merchants in different parts of
      the country, for the use of dealers who sell to them.

   Mercantile marine, the persons and vessels employed in
      commerce, taken collectively.

   Mercantile paper, the notes or acceptances given by
      merchants for goods bought, or received on consignment;
      drafts on merchants for goods sold or consigned.
      --McElrath.
      [1913 Webster]

   Syn: Mercantile, Commercial.

   Usage: Commercial is the wider term, being sometimes used to
          embrace mercantile. In their stricter use, commercial
          relates to the shipping, freighting, forwarding, and
          other business connected with the commerce of a
          country (whether external or internal), that is, the
          exchange of commodities; while mercantile applies to
          the sale of merchandise and goods when brought to
          market. As the two employments are to some extent
          intermingled, the two words are often interchanged.
          [1913 Webster]

WordNet (r) 3.0 (2006):

mercantile agency
    n 1: an organization that provides businesses with credit
         ratings of other firms; "Dun & Bradstreet is the largest
         mercantile agency in the United States" [syn: mercantile
         agency, commercial agency]