The Collaborative International Dictionary of English v.0.48:

Mortification \Mor`ti*fi*ca"tion\, n. [F., fr. L. mortificatio a
   killing. See Mortify.]
   1. The act of mortifying, or the condition of being
      mortified; especially:
      (a) (Med.) The death of one part of an animal body, while
          the rest continues to live; loss of vitality in some
          part of a living animal; gangrene. --Dunglison.
      (b) (Alchem. & Old Chem.) Destruction of active qualities;
          neutralization. [Obs.] --Bacon.
      (c) Subjection of the passions and appetites, by penance,
          abstinence, or painful severities inflicted on the
          body.
          [1913 Webster]

                The mortification of our lusts has something in
                it that is troublesome, yet nothing that is
                unreasonable.                     --Tillotson.
          [1913 Webster]

   2. Deep humiliation or shame, from a loss of pride; painful
      embarassment, usually arising from exposure of a mistake;
      chagrin; vexation.
      [1913 Webster +PJC]

   3. That which mortifies; the cause of humiliation, chagrin,
      or vexation.
      [1913 Webster]

            It is one of the vexatious mortifications of a
            studious man to have his thoughts discovered by a
            tedious visit.                        --L'Estrange.
      [1913 Webster]

   4. (Scots Law) A gift to some charitable or religious
      institution; -- nearly synonymous with mortmain.
      [1913 Webster]

   Syn: Chagrin; vexation; shame. See Chagrin.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mortmain \Mort"main`\, n. [F. mort, morte, dead + main hand; F.
   main-morte. See Mortal, and Manual.] (Law)
   Possession of lands or tenements in, or conveyance to, dead
   hands, or hands that cannot alienate.
   [1913 Webster]

   Note: The term was originally applied to conveyance of land
         made to ecclesiastical bodies; afterward to conveyance
         made to any corporate body. --Burrill.
         [1913 Webster]

WordNet (r) 3.0 (2006):

mortmain
    n 1: real property held inalienably (as by an ecclesiastical
         corporation) [syn: mortmain, dead hand]
    2: the oppressive influence of past events or decisions [syn:
       dead hand, dead hand of the past, mortmain]

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

MORTMAIN. An unlawful alienation of lands, or tenements to any corporation,
sole or aggregate, ecclesiastical or temporal. These purchases having been
chiefly made by religious houses, in consequence of which lands became
perpetually inherent in one dead hand, this has occasioned the general
appellation of mortmain to be applied to such alienations. 2 Bl. Com. 268;
Co. Litt. 2 b; Ersk. Inst. B. 2, t. 4, s. 10; Barr. on the Stat. 27, 97.
     2. Mortmain is also employed to designate all prohibitory laws, which
limit, restrain, or annul gifts, grants, or devises of lands and other
corporeal hereditaments to charitable uses. 2 Story, Eq. Jur. Sec. 1137,
note 1. See Shelf. on Mortm. 2, 3.