The Collaborative International Dictionary of English v.0.48:

Interpellation \In`ter*pel*la"tion\, n. [L. interpellatio: cf.
   F. interpellation.]
   [1913 Webster]
   1. The act of interpelling or interrupting; interruption.
      "Continual interpellations." --Bp. Hall.
      [1913 Webster]

   2. The act of interposing or interceding; intercession.
      [1913 Webster]

            Accepted by his interpellation and intercession.
                                                  --Jer. Taylor.
      [1913 Webster]

   3. An act of interpellating, or of demanding of an officer an
      explanation of his action; imperative or peremptory
      questioning; a point raised in a debate.
      [1913 Webster]

   4. A official summons or citation. --Ayliffe.
      [1913 Webster]

WordNet (r) 3.0 (2006):

interpellation
    n 1: (parliament) a parliamentary procedure of demanding that a
         government official explain some act or policy
    2: the action of interjecting or interposing an action or remark
       that interrupts [syn: interjection, interposition,
       interpolation, interpellation]