The Collaborative International Dictionary of English v.0.48:

Inquiry \In*quir"y\, n.; pl. Inquiries. [See Inquire.]
   [Written also enquiry.]
   1. The act of inquiring; a seeking for information by asking
      questions; interrogation; a question or questioning.
      [1913 Webster]

            He could no path nor track of foot descry,
            Nor by inquiry learn, nor guess by aim. --Spenser.
      [1913 Webster]

            The men which were sent from Cornelius had made
            inquiry for Simon's house, and stood before the
            gate.                                 --Acts x. 17.
      [1913 Webster]

   2. Search for truth, information, or knowledge; examination
      into facts or principles; research; investigation; as,
      physical inquiries.
      [1913 Webster]

            All that is wanting to the perfection of this art
            will undoubtedly be found, if able men . . . will
            make inquiry into it.                 --Dryden.
      [1913 Webster]

   Court of inquiry. See under Court.

   Writ of inquiry, a writ issued in certain actions at law,
      where the defendant has suffered judgment to pass against
      him by default, in order to ascertain and assess the
      plaintiff's damages, where they can not readily be
      ascertained by mere calculation. --Burrill.

   Syn: Interrogation; interrogatory; question; query; scrutiny;
        investigation; research; examination.
        [1913 Webster]

WordNet (r) 3.0 (2006):

inquiry
    n 1: a search for knowledge; "their pottery deserves more
         research than it has received" [syn: inquiry, enquiry,
         research]
    2: 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,
       interrogation] [ant: answer]
    3: a systematic investigation of a matter of public interest
       [syn: inquiry, enquiry]

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "inquiry":
   amassing evidence, assize, audit, bone of contention, canvass,
   catechism, catechizing, change of venue, check, close inquiry,
   consumer research, consumer-preference survey, court-martial,
   cross-examination, cross-interrogatory, cross-question,
   debating point, delving, demand, department of investigation,
   detection, detective work, enquiry, examination, exhaustive study,
   exploration, feeler, hearing, indagation, inquest, inquirendo,
   inquisition, inspection, interrogation, interrogative,
   interrogatory, investigation, investigative bureau, issue,
   jury trial, leader, leading question, legislative investigation,
   legwork, mistrial, moot point, opinion poll, perscrutation,
   point at issue, point in question, poll, probe, probing, problem,
   public-opinion poll, query, querying, quest, question,
   question at issue, question mark, questionary, questioning,
   questionnaire, quodlibet, research, scrutiny, search, sifting,
   sleuthing, study, survey, topic, trial, trial balloon,
   trial by jury, vexed question, witch-hunt



Bouvier's Law Dictionary, Revised 6th Ed (1856):

INQUIRY, WRIT OF. A writ of inquiry is one issued where a judgment has been
entered in a case sounding in damages, without any particular amount being
ascertained; this writ is for the purpose of ascertaining the amount to
which the plaintiff is entitled. Vide Writ Of Inquiry.