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.
      [1913 Webster]

   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.
      [1913 Webster]

            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]

The Collaborative International Dictionary of English v.0.48:

Council \Coun"cil\ (koun"s[i^]l), n. [F. concile, fr. L.
   concilium; con- + calare to call, akin to Gr. ??? to call,
   and E. hale, v., haul. Cf. Conciliate. This word is often
   confounded with counsel, with which it has no connection.]
   [1913 Webster]
   1. An assembly of men summoned or convened for consultation,
      deliberation, or advice; as, a council of physicians for
      consultation in a critical case.
      [1913 Webster]

   2. A body of man elected or appointed to constitute an
      advisory or a legislative assembly; as, a governor's
      council; a city council.
      [1913 Webster]

            An old lord of the council rated me the other day.
                                                  --Shak.
      [1913 Webster]

   3. Act of deliberating; deliberation; consultation.
      [1913 Webster]

            Satan . . . void of rest,
            His potentates to council called by night. --Milton.
      [1913 Webster]

            O great in action and in council wise. --Pope.
      [1913 Webster]

   Aulic council. See under Aulic.

   Cabinet council. See under Cabinet.

   City council, the legislative branch of a city government,
      usually consisting of a board of aldermen and common
      council, but sometimes otherwise constituted.

   Common council. See under Common.

   Council board, Council table, the table round which a
      council holds consultation; also, the council itself in
      deliberation.

   Council chamber, the room or apartment in which a council
      meets.

   Council fire, the ceremonial fire kept burning while the
      Indians hold their councils. [U.S.] --Bartlett.

   Council of war, an assembly of officers of high rank,
      called to consult with the commander in chief in regard to
      measures or importance or nesessity.

   Ecumenical council (Eccl.), an assembly of prelates or
      divines convened from the whole body of the church to
      regulate matters of doctrine or discipline.

   Executive council, a body of men elected as advisers of the
      chief magistrate, whether of a State or the nation. [U.S.]


   Legislative council, the upper house of a legislature,
      usually called the senate.

   Privy council. See under Privy. [Eng.]

   Syn: Assembly; meeting; congress; diet; parliament;
        convention; convocation; synod.
        [1913 Webster]

WordNet (r) 3.0 (2006):

privy council
    n 1: an advisory council to a ruler (especially to the British
         Crown)

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "privy council":
   British Cabinet, Sanhedrin, US Cabinet, advisory body,
   advisory council, assembly, association, bench, board,
   body of advisers, borough council, brain trust, cabinet, camarilla,
   chamber, city council, common council, conference, congress,
   consultative assembly, council, council fire, council of ministers,
   council of state, council of war, county council, court,
   deliberative assembly, diet, directory, divan, junta,
   kitchen cabinet, legislature, ministry, parish council,
   shadow cabinet, soviet, staff, syndicate, synod, tribunal



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

PRIVY COUNCIL, Eng. law. A council of state composed of the king and of such
persons as he may select.