What is Mandamus?

Legal Definition
Mandamus ("We command") is a judicial remedy in the form of an order from a superior court, to any government subordinate court, corporation, or public authority—to do (or forbear from doing) some specific act which that body is obliged under law to do (or refrain from doing)—and which is in the nature of public duty, and in certain cases one of a statutory duty. It cannot be issued to compel an authority to do something against statutory provision. For example, it cannot be used to force a lower court to reject or authorize applications that have been made, but if the court refuses to rule one way or the other then a mandamus can be used to order the court to rule on the applications.

Mandamus may be a command to do an administrative action or not to take a particular action, and it is supplemented by legal rights. In the American legal system it must be a judicially enforceable and legally protected right before one suffering a grievance can ask for a mandamus. A person can be said to be aggrieved only when he is denied a legal right by someone who has a legal duty to do something and abstains from doing it.
-- Wikipedia
Legal Definition
A (writ of) mandamus is an order from a court to an inferior government official ordering the government official to properly fulfill their official duties or correct an abuse of discretion. (See, e.g. Cheney v. United States Dist. Court For D.C. (03-475) 542 U.S. 367 (2004) 334 F.3d 1096.)

Rules on mandamus and similar orders vary by jurisdiction. In the federal courts, these orders most frequently appear when a party to a suit wants to appeal a judge's decision but is blocked by rules against interlocutory appeals. Instead of appealing directly, the party simply sues the judge, seeking a mandamus compelling the judge to correct his earlier mistake. Generally, this type of indirect appeal is only available if the party has no alternative means of seeking review.

See Civil Procedure
Legal Definition
Practice. The name of a writ, the principal word of which when the proceedings were in Latin, was mandamus, we command.

2. It is a command issuing in the name of the sovereign authority from a superior court having jurisdiction, and is directed to some person, corporation, or, inferior court, within the jurisdiction of such superior court, requiring them to do some particular thing therein specified, which appertains to their office and duty, and which the superior court has previously determined, or at least supposes to be consonant to right and justice. 20 Pick. 484; 21 Pick. 258; Dudley, 37; 4 Humph. 437.

3. Mandamus is not a writ of right, it is not consequently granted of course, but only at the discretion of the court to whom the application for it is made; and this discretion is not exercised in favor of the applicant, unless some just and useful purpose may be answered by the writ. 2 T. R. 385; 1 Cowen's R. 501; 11 Shepl. 151; 1 Pike, 11.

4. This writ was introduced io prevent disorders from a failure of justice; therefore it ought to be used upon all occasions where the law has established no specific remedy, and where in justice and good government there ought to be one. 3 Burr. R. 1267; 1 T. R. 148, 9.; 2 Pick. 414; 4 Pick. 68; 10 Pick. 235, 244; 7 Mass; 340; 3 Binn. 273; 5 Halst. 57; Cooke, 160; 1 Wend. 318; 5 Pet. 190; 1 Caines, R. 511; John. Cas. 181; 12 Wend. 183; 8 Pet. 291; 12 Pet. 524; 2 Penning. 1024; Hardin, 172; 7 Wheat. 534; 5 Watts. 152; 2 H. & M. 132; 3 H. & M. 1; 1 S. & R. 473; 5 Binn. 87; 3 Conn. 243; 2 Virg. Cas. 499; 5 Call. 548. Mandamus will not lie where the law has given another specific remedy. 1 Wend. 318; 10 John. 484; 1 Cow. 417; Coleman, 117; 1 Pet. 567; 2 Cowen, 444; 2 M'Cord, 170; Minor, 46; 2 Leigh, 165; Const. Rep. 165, 175, 703.

5. The 13th section of the act of congress of September, 24, 1789, gives the supreme court power to issue writs of mandamus in cases warranted by the principles and usages of law, to any courts appointed or persons holding office, under the authority of the United States. The issuing of a mandamus to courts, is the exercise of an appellate jurisdiction, and, therefore constitutionally vested in the supreme court; but a mandamus directed to a public officer, belongs to original jurisdiction, and by the constitution, the exercise of original jurisdiction by the supreme court is restricted to certain specified cases, which do not comprehend a mandamus. The latter clause of the above section, authorizing this writ to be issued by the supreme court, to persons holding office under the authority of the United States, is, therefore, not warranted by the constitution, and void. 1 Cranch, R. 175.

6. The circuit courts of the United States may also issue writs of mandamus, but their power in this particular, is confined exclusively to those cases in which it may be necessary to the exercise of their jurisdiction. 7 Cranch, R. 504; 8 Wheat. R. 598; 1 Paine's R. 453. Vide, generally, 3 Bl. Com. 110; Com. Dig. h. t; Bac. Ab. h. t.; Vin. Ab. h. t.; Selw. N. P. h. t.; Chit. Pr. h. t.; Serg. Const. Index, h. t.; Ang. on Corp. Index, h. t.; 3 Chit. Bl. Com. 265 n. 7; 1 Kent. Com. 322; Dane's Ab. Index, h. t.; 6 Watts & Serg. 386, 397; Bouv. Inst. Index, h. t.; and the article "Courts of the United States."
-- Bouviers Law Dictionary
Legal Definition
Lat. We command. This is the name of a writ (formerly a high prerogative writ) which issues from a court of superior jurisdiction, and is directed to a private or municipal corporation or any of its officers or to an executive, administrative or judicial officer or to an inferior court, commanding the performance of a particular act therein specified, and belonging to his or their public, official or ministerial duty or directing the restoration of the complainant to rights or privileges of which he has been illegally deprived. See Lahiff v. St. Joseph, etc., Soc., 76 Conn. 648, 57 AH. 692, 65 L. In A. 92, 100 Am. St. Rep. 1012; Milster v. Spartanburg, 68 S. C. 248, 47 S. E. 141; State v. Carpenter, 51 Ohio St 83, 37 N. E. 261, 46 Am. St. Rep. 556; Chicago & N. W. R. Co. v. Chane, 113 U. S. 424, 5 Sup. Ct. 578, 28 L. Eld. 1064; Arnold v. Kennebec County, 93 Me. 117, 44 Atl. 364; Placard v. State, 148 Ind. 305, 47 N. E. 623; AUanta v. Wright, 119 Ga. 207, 45 S. E. 994; State v. Lewis, 76 Mo. 370; Etx parte Crane, 5 Pet 190, 8 L. Ed. 92; Marbury v. Madison, 1 Cranch, 158, 2 L. Ed. 60; In S. v. Butterworth, 169 U. S. 600, 18 Sup. Ct 441, 42 L. Ed. 873. The action of mandamus is one, brought in a court of competent jurisdiction, to obtnin an order of such court commanding an inferior tribunal, board, corporation, or person to do or not to do an act the performance or omission of which the law enjoins as a duty resulting from an office, trust, or station. Where discretion is left to the inferior tribunal or person, the mandamus can only compel it to act, but cannot control such discretion. Rev. Code Iowa, 1880, § 3373. Classification. The writ of mandamus is either peremptory or alternative, according as it requires the defendant absolutely to obey its behest, or gives him an opportunity to show cause to the contrary. It is the usual practice to issue the alternative writ first. This commands the defendant to do the particular act, or else to appear and show cause against it at a day named. If he neglects to obey the writ, and either makes default in his appearance or fails to show good cause against the application, the peremptory mandamus issues, which commands him absolutely and without qualification to do the act.
-- Black's Law Dictionary
Legal Definition
A command issued from a court directed to some person, corporation or inferior court within the jurisdiction of the superior court requiring such person, corporation or inferior court to do some particular thing therein specified. See 7 Houst. (Del.) 338, 40 Am. St. Rep. 127, 32 Atl. 143.
-- Ballentine's Law Dictionary