The Collaborative International Dictionary of English v.0.48:

Merchant \Mer"chant\, a.
   Of, pertaining to, or employed in, trade or merchandise; as,
   the merchant service.
   [1913 Webster]

   Merchant bar, Merchant iron or Merchant steel, certain
      common sizes of wrought iron and steel bars.

   Merchant service or Merchant marine, the mercantile marine
      of a country. --Am. Cyc.

   Merchant ship, a ship employed in commerce.

   Merchant tailor, a tailor who keeps and sells materials for
      the garments which he makes.
      [1913 Webster]

WordNet (r) 3.0 (2006):

merchant ship
    n 1: a cargo ship; "they did much of their overseas trade in
         foreign bottoms" [syn: bottom, freighter,
         merchantman, merchant ship]