The Collaborative International Dictionary of English v.0.48:

Convocation \Con`vo*ca"tion\, n. [L. convocatio: cf. F.
   convocation. See Convoke.]
   1. The act of calling or assembling by summons.
      [1913 Webster]

   2. An assembly or meeting.
      [1913 Webster]

            In the first day there shall be a holy convocation.
                                                  --Ex. xii. 16.
      [1913 Webster]

   3. (Ch. of Eng.) An assembly of the clergy, by their
      representatives, to consult on ecclesiastical affairs.
      [1913 Webster]

   Note: In England, the provinces of Canterbury and York have
         each their convocation, but no session for business
         were allowed from 1717 to 1861. The Convocation of
         Canterbury consists of two houses. In the Convocation
         of York the business has been generally conducted in
         one assembly.
         [1913 Webster]

   4. (Oxf. University) An academical assembly, in which the
      business of the university is transacted.

   Syn: meeting; assembly; congregation; congress; diet;
        convention; synod; council.
        [1913 Webster]

WordNet (r) 3.0 (2006):

convocation
    n 1: a group gathered in response to a summons
    2: the act of convoking [syn: convocation, calling together]

Moby Thesaurus II by Grady Ward, 1.0:

107 Moby Thesaurus words for "convocation":
   Council of Nicaea, Council of Trent, Lateran Council,
   Vatican Council, assemblee, assembly, assignation, at home,
   baccalaureate service, ball, beck, beck and call, bidding, brawl,
   call, calling, calling forth, caucus, celebration, ceremonial,
   ceremony, chapter, classis, colloquium, commencement, commission,
   committee, conciliarism, conclave, concourse, conference,
   congregation, congress, consistory, conventicle, convention,
   council, dance, date, diet, diocesan conference,
   ecclesiastical council, ecumenical council, eisteddfod,
   empty formality, evocation, exercise, exercises, festivity, fete,
   forgathering, formal, formality, forum, function, gathering,
   get-together, graduation, graduation exercises, housewarming,
   inaugural, inauguration, indent, initiation, invocation, levee,
   liturgy, meet, meeting, mummery, nod, observance, office, panel,
   parochial church council, parochial council, party, performance,
   plenary council, plenum, preconization, presbytery, prom, quorum,
   rally, reception, religious ceremony, rendezvous, requisition,
   rite, rite de passage, rite of passage, ritual, seance, service,
   session, shindig, sit-in, sitting, soiree, solemnity,
   solemnization, summons, symposium, synod, turnout, vestry



Easton's 1897 Bible Dictionary:

Convocation
   a meeting of a religious character as distinguished from
   congregation, which was more general, dealing with political and
   legal matters. Hence it is called an "holy convocation." Such
   convocations were the Sabbaths (Lev. 23:2, 3), the Passover (Ex.
   12:16; Lev. 23:7, 8; Num. 28:25), Pentecost (Lev. 23:21), the
   feast of Trumpets (Lev. 23:24; Num. 29:1), the feast of Weeks
   (Num. 28:26), and the feast of Tabernacles (Lev. 23:35, 36). The
   great fast, the annual day of atonement, was "the holy
   convocation" (Lev. 23:27; Num. 29:7).


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

CONVOCATION, eccles. law. This word literally signifies called together. The
assembly of the representatives of the clergy. As to the powers of
convocations, see Shelf. on M. & D. 23., See Court of Convocation.