And below is what I'd call a pretty official definition:

http://legal-dictionary.thefreedictionary.com/show cause ord...

A court order, made upon the motion of an applicant, that requires a party to appear and provide reasons why the court should not perform or not allow a particular action and mandates this party to meet the Prima Facie case set forth in the complaint or Affidavit of the applicant.

A show cause order, also called an order to show cause, mandates that an individual or corporation make a court appearance to explain why the court should not take a proposed action. A court issues this type of order upon the application of a party requesting specific relief and providing the court with an affidavit or declaration (a sworn or affirmed statement alleging certain facts). A show cause order is generally used in Contempt actions, cases involving injunctive relief, and situations where time is of the essence.

A show cause order can be viewed as an accelerated motion. A motion is an application to the court for an order that seeks answers to questions that are collateral to the main object of the action. For example, in a civil lawsuit the plaintiff generally requests from the defendant

documents pertinent to the case. If the defendant refuses to provide the documents or does not make a timely response to the request, the plaintiff may file a motion with the court asking that it issue an order to compel the defendant to produce the documents.

A show cause order is similar to a motion but it can produce a court order on the requested relief much more quickly than a motion can. For example, after a motion is served on the opposing party, that party has a certain number of days under the jurisdiction's rules of Civil Procedure to prepare a response. A show cause order is submitted to a judge, who reads the applicant's papers and decides the deadline for the responding party's submission of papers. The judge may order an opposing party to appear "forthwith" in urgent cases. The judge may hear arguments on the matter at some place other than the courthouse, if necessary, and may allow papers to be served on opposing parties by a method not ordinarily permitted.

A judge may include in the show cause order a Temporary Restraining Order or stay that maintains the status quo as long as the matter is pending before the court. At the hearing on the show cause order, if the responding party fails to rebut the prima facie case (evidence sufficient to establish a fact if uncontradicted) made by the applicant, the court will grant the relief sought by the applicant.
West's Encyclopedia of American Law, edition 2. Copyright 2008 The Gale Group, Inc. All rights reserved.

show cause order ("order to show cause" or "OSC) n. an order of the court directing a party to a lawsuit to appear on a certain date to show cause why the judge should not issue a specific order or make a certain finding. Examples: to show cause why the wife in a divorce action should not be awarded $1,000 a month alimony (spousal support) and $500 a month child support, why the husband should not be ordered to stay away, and why the wife should not have temporary custody of their child. (See: order to show cause)