The Collaborative International Dictionary of English v.0.48:

Enormity \E*nor"mi*ty\, n.; pl. Enormities. [L. enormitas, fr.
   enormis enormous: cf. F. ['e]normit['e]. See Enormous.]
   1. The state or quality of exceeding a measure or rule, or of
      being immoderate, monstrous, or outrageous.
      [1913 Webster]

            The enormity of his learned acquisitions. --De
                                                  Quincey.
      [1913 Webster]

   2. That which is enormous; especially, an exceeding offense
      against order, right, or decency; an atrocious crime;
      flagitious villainy; an atrocity.
      [1913 Webster]

            These clamorous enormities which are grown too big
            and strong for law or shame.          --South.
      [1913 Webster]

WordNet (r) 3.0 (2006):

enormity
    n 1: the quality of being outrageous [syn: outrageousness,
         enormity]
    2: vastness of size or extent; "in careful usage the noun
       enormity is not used to express the idea of great size";
       "universities recognized the enormity of their task"
    3: the quality of extreme wickedness
    4: an act of extreme wickedness