The Collaborative International Dictionary of English v.0.48:

Privy \Priv"y\, a. [F. priv['e], fr. L. privatus. See
   Private.]
   [1913 Webster]
   1. Of or pertaining to some person exclusively; assigned to
      private uses; not public; private; as, the privy purse. "
      Privee knights and squires." --Chaucer.
      [1913 Webster]

   2. Secret; clandestine. " A privee thief." --Chaucer.
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   3. Appropriated to retirement; private; not open to the
      public. " Privy chambers." --Ezek. xxi. 14.
      [1913 Webster]

   4. Admitted to knowledge of a secret transaction; secretly
      cognizant; privately knowing.
      [1913 Webster]

            His wife also being privy to it.      --Acts v. 2.
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            Myself am one made privy to the plot. --Shak.
      [1913 Webster]

   Privy chamber, a private apartment in a royal residence.
      [Eng.]

   Privy council (Eng. Law), the principal council of the
      sovereign, composed of the cabinet ministers and other
      persons chosen by the king or queen. --Burrill.

   Privy councilor, a member of the privy council.

   Privy purse, moneys set apart for the personal use of the
      monarch; also, the title of the person having charge of
      these moneys. [Eng.] --Macaulay.

   Privy seal or Privy signet, the seal which the king uses
      in grants, etc., which are to pass the great seal, or
      which he uses in matters of subordinate consequence which
      do not require the great seal; also, elliptically, the
      principal secretary of state, or person intrusted with the
      privy seal. [Eng.]

   Privy verdict, a verdict given privily to the judge out of
      court; -- now disused. --Burrill.
      [1913 Webster]

WordNet (r) 3.0 (2006):

privy purse
    n 1: allowance for a monarch's personal expenses