Easton's Bible Dictionary
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 (Leviticus 23:2, 3), the Passover (Exodus 12:16; Leviticus 23:7, 8; Numbers 28:25), Pentecost (Leviticus 23:21), the feast of Trumpets (Leviticus 23:24; Numbers 29:1), the feast of Weeks (Numbers 28:26), and the feast of Tabernacles (Leviticus 23:35, 36). The great fast, the annual day of atonement, was "the holy convocation" (Leviticus 23:27; Numbers 29:7).
Noah Webster's New International Dictionary of the English Language
1. (n.) The act of calling or assembling by summons.
2. (n.) An assembly or meeting.
3. (n.) An assembly of the clergy, by their representatives, to consult on ecclesiastical affairs.
4. (n.) An academic assembly, in which the business of the university is transacted.