Source : Webster's Revised Unabridged Dictionary (1913)

Intercession \In`ter*ces"sion\, n. [L. intercessio an
   intervention, a becoming surety: cf. F. intercession. See
   {Intercede}.]
   The act of interceding; mediation; interposition between
   parties at variance, with a view to reconcilation; prayer,
   petition, or entreaty in favor of, or (less often) against,
   another or others.

         But the Spirit itself maketh intercession for us with
         groanings which can not be uttered.      --Rom. viii.
                                                  26.

Source : WordNet®

intercession
     n 1: a prayer to God on behalf of another person
     2: the act of intervening (as to mediate a dispute) [syn: {intervention}]