The Collaborative International Dictionary of English v.0.48:

Maidenhead \Maid"en*head\, n. [See Maidenhood.]
   1. The state of being a maiden; maidenhood; virginity.
      --Shak.
      [1913 Webster]

   2. The state of being unused or uncontaminated; freshness;
      purity. [Obs.]
      [1913 Webster]

            The maidenhead of their credit.       --Sir H.
                                                  Wotton.
      [1913 Webster]

   3. The hymen, or virginal membrane.
      [1913 Webster]

WordNet (r) 3.0 (2006):

maidenhead
    n 1: a fold of tissue that partly covers the entrance to the
         vagina of a virgin [syn: hymen, maidenhead, virginal
         membrane]