The Collaborative International Dictionary of English v.0.48:

Amortization \A*mor`ti*za"tion\, n. [LL. amortisatio,
   admortizatio. See Amortize, and cf. Admortization.]
   1. (Law) The act or right of alienating lands to a
      corporation, which was considered formerly as transferring
      them to dead hands, or in mortmain.
      [1913 Webster]

   2. The extinction of a debt, usually by means of a sinking
      fund; also, the money thus paid. --Simmonds.
      [1913 Webster]

WordNet (r) 3.0 (2006):

amortization
    n 1: the reduction of the value of an asset by prorating its
         cost over a period of years [syn: amortization,
         amortisation]
    2: payment of an obligation in a series of installments or
       transfers [syn: amortization, amortisation]