The Collaborative International Dictionary of English v.0.48:

buying \buying\ n.
   the act of buying; as, buying equipment for the trip took
   several hours.

   Syn: purchasing.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Buy \Buy\ (b[imac]), v. t. [imp. & p. p. Bought (b[add]t); p.
   pr. & vb. n. Buying (b[imac]"[i^]ng).] [OE. buggen, buggen,
   bien, AS. bycgan, akin to OS. buggean, Goth. bugjan.]
   1. To acquire the ownership of (property) by giving an
      accepted price or consideration therefor, or by agreeing
      to do so; to acquire by the payment of a price or value;
      to purchase; -- opposed to sell.
      [1913 Webster]

            Buy what thou hast no need of, and ere long thou
            wilt sell thy necessaries.            --B. Franklin.
      [1913 Webster]

   2. To acquire or procure by something given or done in
      exchange, literally or figuratively; to get, at a cost or
      sacrifice; to buy pleasure with pain.
      [1913 Webster]

            Buy the truth and sell it not; also wisdom, and
            instruction, and understanding.       --Prov. xxiii.
                                                  23.
      [1913 Webster]

   To buy again. See Againbuy. [Obs.] --Chaucer.

   To buy off.
      (a) To influence to compliance; to cause to bend or yield
          by some consideration; as, to buy off conscience.
      (b) To detach by a consideration given; as, to buy off one
          from a party.

   To buy out
      (a) To buy off, or detach from. --Shak.
      (b) To purchase the share or shares of in a stock, fund,
          or partnership, by which the seller is separated from
          the company, and the purchaser takes his place; as, A
          buys out B.
      (c) To purchase the entire stock in trade and the good
          will of a business.

   To buy in, to purchase stock in any fund or partnership.

   To buy on credit, to purchase, on a promise, in fact or in
      law, to make payment at a future day.

   To buy the refusal (of anything), to give a consideration
      for the right of purchasing, at a fixed price, at a future
      time.
      [1913 Webster]

WordNet (r) 3.0 (2006):

buying
    n 1: the act of buying; "buying and selling fill their days";
         "shrewd purchasing requires considerable knowledge" [syn:
         buying, purchasing]