The Collaborative International Dictionary of English v.0.48:

Prayer \Prayer\ (?; 277), n. [OE. preiere, OF. preiere, F.
   pri[`e]re, fr. L. precarius obtained by prayer, fr. precari
   to pray. See Pray, v. i.]
   1. The act of praying, or of asking a favor; earnest request
      or entreaty; hence, a petition or memorial addressed to a
      court or a legislative body. "Their meek preyere."
      --Chaucer
      [1913 Webster]

   2. The act of addressing supplication to a divinity,
      especially to the true God; the offering of adoration,
      confession, supplication, and thanksgiving to the Supreme
      Being; as, public prayer; secret prayer.
      [1913 Webster]

            As he is famed for mildness, peace, and prayer.
                                                  --Shak.
      [1913 Webster]

   3. The form of words used in praying; a formula of
      supplication; an expressed petition; especially, a
      supplication addressed to God; as, a written or
      extemporaneous prayer; to repeat one's prayers.
      [1913 Webster]

            He made those excellent prayers which were published
            immediately after his death.          --Bp. Fell.
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   Prayer book, a book containing devotional prayers.

   Prayer meeting, a meeting or gathering for prayer to God.
      [1913 Webster]

   Syn: Petition; orison; supplication; entreaty; suit.
        [1913 Webster]

WordNet (r) 3.0 (2006):

prayer meeting
    n 1: a service at which people sing hymns and pray together
         [syn: prayer meeting, prayer service]