The Collaborative International Dictionary of English v.0.48:

Bargain \Bar"gain\, n. [OE. bargayn, bargany, OF. bargaigne,
   bargagne, prob. from a supposed LL. barcaneum, fr. barca a
   boat which carries merchandise to the shore; hence, to
   traffic to and fro, to carry on commerce in general. See
   Bark a vessel. ]
   1. An agreement between parties concerning the sale of
      property; or a contract by which one party binds himself
      to transfer the right to some property for a
      consideration, and the other party binds himself to
      receive the property and pay the consideration.
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            A contract is a bargain that is legally binding.
                                                  --Wharton.
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   2. An agreement or stipulation; mutual pledge.
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            And whon your honors mean to solemnize
            The bargain of your faith.            --Shak.
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   3. A purchase; also ( when not qualified), a gainful
      transaction; an advantageous purchase; as, to buy a thing
      at a bargain.
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   4. The thing stipulated or purchased; also, anything bought
      cheap.
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            She was too fond of her most filthy bargain. --Shak.
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   Bargain and sale (Law), a species of conveyance, by which
      the bargainor contracts to convey the lands to the
      bargainee, and becomes by such contract a trustee for and
      seized to the use of the bargainee. The statute then
      completes the purchase; i. e., the bargain vests the use,
      and the statute vests the possession. --Blackstone.

   Into the bargain, over and above what is stipulated;
      besides.

   To sell bargains, to make saucy (usually indelicate)
      repartees. [Obs.] --Swift.

   To strike a bargain, to reach or ratify an agreement. "A
      bargain was struck." --Macaulay.
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   Syn: Contract; stipulation; purchase; engagement.
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WordNet (r) 3.0 (2006):

into the bargain
    adv 1: in addition; over and above what is expected; "He lost
           his wife in the bargain" [syn: in the bargain, into
           the bargain]