The Collaborative International Dictionary of English v.0.48:

Mortgage \Mort"gage\ (m[^o]r"g[asl]j; 48), n. [F. mort-gage;
   mort dead (L. mortuus) + gage pledge. See Mortal, and
   Gage.]
   1. (Law) A conveyance of property, upon condition, as
      security for the payment of a debt or the preformance of a
      duty, and to become void upon payment or performance
      according to the stipulated terms; also, the written
      instrument by which the conveyance is made.
      [1913 Webster]

   Note: It was called a mortgage (or dead pledge) because,
         whatever profit it might yield, it did not thereby
         redeem itself, but became lost or dead to the mortgager
         upon breach of the condition. But in equity a right of
         redemption is an inseparable incident of a mortgage
         until the mortgager is debarred by his own laches, or
         by judicial decree. --Cowell. --Kent.
         [1913 Webster]

   2. State of being pledged; as, lands given in mortgage.
      [1913 Webster]

   Chattel mortgage. See under Chattel.

   To foreclose a mortgage. See under Foreclose.

   Mortgage deed (Law), a deed given by way of mortgage.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mortgage deed
    n 1: deed embodying a mortgage