The Collaborative International Dictionary of English v.0.48:

Freighter \Freight"er\, n.
   1. One who loads a ship, or one who charters and loads a
      ship.
      [1913 Webster]

   2. One employed in receiving and forwarding freight.
      [1913 Webster]

   3. One for whom freight is transported.
      [1913 Webster]

   4. A vessel used mainly to carry freight.
      [1913 Webster]

WordNet (r) 3.0 (2006):

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