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]

Moby Thesaurus II by Grady Ward, 1.0:

121 Moby Thesaurus words for "freighter":
   Amtrak, Aquarius, Ganymede, Hebe, argosy, ark, baggage train,
   bathyscaphe, bearer, bheesty, busboy, cable railroad, caddie,
   caravel, cargo handler, cargo ship, carrier, carrier pigeon,
   carter, choo-choo, coast guard cutter, coaster, cog railroad,
   cog railway, collier, common carrier, conveyer, coolie, cupbearer,
   derelict, drayman, dredge, el, electric, electric train, elevated,
   express, express train, expressman, fishing boat, flier, freight,
   freight train, funicular, goods train, gun bearer, hauler,
   homing pigeon, hydrofoil, icebreaker, interurban, lash,
   letter carrier, lightning express, lightship, limited, liner,
   litter-bearer, local, merchant ship, merchantman, metro,
   milk train, monorail, oiler, packet, packet boat, paddle steamer,
   parliamentary, parliamentary train, passenger train, picket ship,
   porter, rack-and-pinion railroad, railroad train, rattler, redcap,
   refrigeration ship, revenue cutter, rolling stock, rotor,
   rotor ship, screw steamer, self-propelled barge, shield-bearer,
   ship, shuttle, shuttle train, side-wheeler, skycap, slaver,
   spar-decker, special, steam schooner, steam yacht, steamer,
   stern-wheeler, stevedore, storeship, streamliner, stretcher-bearer,
   subway, tanker, tender, the Water Bearer, train, tramp steamer,
   transport, transporter, trawler, truck driver, trucker, tube,
   turbine, underground, wagoner, water boy, water carrier, way train,
   weather ship, whaler



Bouvier's Law Dictionary, Revised 6th Ed (1856):

FREIGHTER, contracts. He to whom a ship or vessel has been hired. 3 Kent,
Com. 173; 3 Pardess. n. 704.
     2. The freighter is entitled to the enjoyment of the vessel according
to contract, and the vessel hired is the only one that he is bound to take
there can, therefore, be no substitution without his consent. When the
vessel has been chartered only in part, the freighter is only entitled to
the space he has contracted for; and in case of his occupying more room or
putting on board a greater weight, he must pay freight on the principles
mentioned under the article of freight.
     3. The freighter is required to use the vessel agreeably to the
provisions of the charter party, or, in the absence of any such provisions,
according to the usages of trade he cannot load the vessel with merchandise
which would render it liable to condemnation for violating the laws of a
foreign state. 3 John. R. 105. The freighter is also required to return the
vessel as soon as the time for which he chartered her has expired, and to
pay the freight.