The Collaborative International Dictionary of English v.0.48:

Defloration \Def`lo*ra"tion\, n. [LL. defloratio: cf. F.
   d['e]floration.]
   1. The act of deflouring; as, the defloration of a virgin.
      --Johnson.
      [1913 Webster]

   2. That which is chosen as the flower or choicest part;
      careful culling or selection. [R.]
      [1913 Webster]

            The laws of Normandy are, in a great measure, the
            defloration of the English laws.      --Sir M. Hale.
      [1913 Webster]

WordNet (r) 3.0 (2006):

defloration
    n 1: an act that despoils the innocence or beauty of something
    2: the act of depriving a woman of her virginity (especially by
       rupturing the hymen through sexual intercourse)

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

DEFLORATION. The act by which a woman is deprived of her virginity.
     2. When this is done unlawfully, and against her will, it bears the
name of rape, (q.v.) when she consents, it is fornication. (q.v.)