1. A writ issued by a court exercising unusual or discretionary power. Examples are writ of certiorari, writ of habeas corpus, writ of mandamus. and prohibition writ. — aka prerogative writ. 
prerogative writs – Writs issued in cases of public right and those affecting the sovereignty of the state, its franchises and prerogatives, or the liberties of its people. State ex rel. Goodwin v Nelson County, 1 ND 88, 45 NW 33; Atty. Gen. v Railroad Co. 35 Wis 513. Writs under which extraordinary remedies are made available. 
writ of habeas corpus – command that a prisoner (or detainee or probatee) be brought before the court to challenge the legality of their custody and demand their release. — aka great writ.
writ of certiorari – issued by an appellate court, directing a lower court to deliver the record in the case for review.
writ of mandamus – issued to compel performance of a particular act by a lower court or a governmental officer or body, usually to correct a prior action or failure to act.
writ of prohibition – issued by an appellate court to prevent a lower court from exceeding jurisdiction or to prevent a nonjudicial officer or entity from exercising a power.
writ of consultation – issued by an appellate court ordering a lower court to proceed in a matter the lower court previously refused to hear.