The Collaborative International Dictionary of English v.0.48:

Purification \Pu`ri*fi*ca"tion\, n. [F. purification, L.
   purificatio. See Purify.]
   1. The act of purifying; the act or operation of separating
      and removing from anything that which is impure or
      noxious, or heterogeneous or foreign to it; as, the
      purification of liquors, or of metals.
      [1913 Webster]

   2. The act or operation of cleansing ceremonially, by
      removing any pollution or defilement.
      [1913 Webster]

            When the days of her purification according to the
            law of Moses were accomplished.       --Luke ii. 22.
      [1913 Webster]

   3. A cleansing from guilt or the pollution of sin; the
      extinction of sinful desires, appetites, and inclinations.
      [1913 Webster]

WordNet (r) 3.0 (2006):

purification
    n 1: the act of cleaning by getting rid of impurities
    2: the process of removing impurities (as from oil or metals or
       sugar etc.) [syn: refining, refinement, purification]
    3: a ceremonial cleansing from defilement or uncleanness by the
       performance of appropriate rites [syn: purification,
       purgation]
    4: the act of purging of sin or guilt; moral or spiritual
       cleansing; "purification through repentance"