Source : Webster's Revised Unabridged Dictionary (1913)

Invocation \In`vo*ca"tion\, n. [F. invocation, L. invocatio.]
   1. The act or form of calling for the assistance or presence
      of some superior being; earnest and solemn entreaty; esp.,
      prayer offered to a divine being.

            Sweet invocation of a child; most pretty and
            pathetical!                           --Shak.

            The whole poem is a prayer to Fortune, and the
            invocation is divided between the two deities.
                                                  --Addison.

   2. (Law) A call or summons; especially, a judicial call,
      demand, or order; as, the invocation of papers or evidence
      into court.

Source : WordNet®

invocation
     n 1: a prayer asking God's help as part of a religious service
          [syn: {supplication}]
     2: an incantation used in conjuring or summoning a devil
     3: calling up a spirit or devil [syn: {conjuring}, {conjuration},
         {conjury}]
     4: the act of appealing for help