The Collaborative International Dictionary of English v.0.48:

Traffic \Traf"fic\, v. i. [imp. & p. p. Trafficked; p. pr. &
   vb. n. Trafficking.] [F. trafiquer; cf. It. trafficare, Sp.
   traficar, trafagar, Pg. traficar, trafegar, trafeguear, LL.
   traficare; of uncertain origin, perhaps fr. L. trans across,
   over + -ficare to make (see -fy, and cf. G. ["u]bermachen
   to transmit, send over, e. g., money, wares); or cf. Pg.
   trasfegar to pour out from one vessel into another, OPg.
   also, to traffic, perhaps fr. (assumed) LL. vicare to
   exchange, from L. vicis change (cf. Vicar).]
   1. To pass goods and commodities from one person to another
      for an equivalent in goods or money; to buy or sell goods;
      to barter; to trade.
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   2. To trade meanly or mercenarily; to bargain.
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The Collaborative International Dictionary of English v.0.48:

Traffic \Traf"fic\, v. t.
   To exchange in traffic; to effect by a bargain or for a
   consideration.
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The Collaborative International Dictionary of English v.0.48:

Traffic \Traf"fic\, n. [Cf. F. trafic, It. traffico, Sp.
   tr['a]fico, tr['a]fago, Pg. tr['a]fego, LL. traficum,
   trafica. See Traffic, v.]
   1. Commerce, either by barter or by buying and selling;
      interchange of goods and commodities; trade.
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            A merchant of great traffic through the world.
                                                  --Shak.
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            The traffic in honors, places, and pardons.
                                                  --Macaulay.
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   Note: This word, like trade, comprehends every species of
         dealing in the exchange or passing of goods or
         merchandise from hand to hand for an equivalent, unless
         the business of relating may be excepted. It signifies
         appropriately foreign trade, but is not limited to
         that.
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   2. Commodities of the market. [R.]
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            You 'll see a draggled damsel
            From Billingsgate her fishy traffic bear. --Gay.
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   3. The business done upon a railway, steamboat line, etc.,
      with reference to the number of passengers or the amount
      of freight carried.
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   Traffic return, a periodical statement of the receipts for
      goods and passengers, as on a railway line.

   Traffic taker, a computer of the returns of traffic on a
      railway, steamboat line, etc.
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WordNet (r) 3.0 (2006):

traffic
    n 1: the aggregation of things (pedestrians or vehicles) coming
         and going in a particular locality during a specified
         period of time
    2: buying and selling; especially illicit trade
    3: the amount of activity over a communication system during a
       given period of time; "heavy traffic overloaded the trunk
       lines"; "traffic on the internet is lightest during the
       night"
    4: social or verbal interchange (usually followed by `with')
       [syn: dealings, traffic]
    v 1: deal illegally; "traffic drugs"
    2: trade or deal a commodity; "They trafficked with us for gold"

Moby Thesaurus II by Grady Ward, 1.0:

99 Moby Thesaurus words for "traffic":
   ESP, answer, balance of trade, bargain, barter, be in,
   big business, black-market, bootleg, business, business dealings,
   buy and sell, carry, change, closeness, commerce,
   commercial affairs, commercial relations, communication, communion,
   congress, connection, contact, conversation, converse, conveyance,
   correspondence, custom, deal, deal in, dealing, dealings,
   do business, exchange, fair trade, familiarity, free trade,
   freight, give in exchange, handle, horse-trade, industry,
   information, interaction, interchange, intercommunication,
   intercommunion, intercourse, interplay, intimacy, job,
   linguistic intercourse, market, marketing, mercantile business,
   merchandise, merchantry, message, moonshine, movement,
   multilateral trade, push, reciprocal trade, relations,
   relationship, reply, response, restraint of trade, retail, sell,
   shipping, shove, small business, social intercourse, speaking,
   speech, speech circuit, speech situation, swap, swap horses,
   switch, take in exchange, talking, telepathy, the business world,
   the marketplace, touch, trade, trade in, trade off,
   trade sight unseen, traffic in, transport, transportation, travel,
   truck, two-way communication, unilateral trade, wholesale



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

TRAFFIC. Commerce, trade, sale or exchange of merchandise, bills, money and
the like.