Source : Webster's Revised Unabridged Dictionary (1913)

Interrogation \In*ter`ro*ga"tion\, n. [L. interrogatio: cf. F.
   interrogation.]
   1. The act of interrogating or questioning; examination by
      questions; inquiry.

   2. A question put; an inquiry.

   3. A point, mark, or sign, thus [?], indicating that the
      sentence with which it is connected is a question. It is
      used to express doubt, or to mark a query. Called also
      {interrogation point}.

Source : WordNet®

interrogation
     n 1: a sentence of inquiry that asks for a reply; "he asked a
          direct question"; "he had trouble phrasing his
          interrogations" [syn: {question}, {interrogative}, {interrogative
          sentence}]
     2: a transmission that will trigger an answering transmission
        from a transponder
     3: formal systematic questioning [syn: {examination}, {interrogatory}]
     4: an instance of questioning; "there was a question about my
        training"; "we made inquiries of all those who were
        present" [syn: {question}, {inquiry}, {enquiry}, {query}]
        [ant: {answer}]