Translated from Latin, mandamus means "we command."
In a legal context, it is the term given to a court order issued to a lesser government entity or someone that holds a lesser government office. It compels the recipient to fulfill a specific duty or rectify a past indiscretion.
A mandamus, or writ of mandamus, can also force the recipient to eschew certain acts in accordance with applicable legal requirements.
The issuance of a mandamus is unusual for two key reasons. First, it can occur while a lower court is still hearing a case. Second, it can occur without being subject to all of the intricacies of judicial procedure.
Even so, there are several circumstances in which a mandamus can and will be issued. For example, a higher court can issue this type of order when a lower court refuses to dismiss a case on applicable grounds, or when it wrongfully denies a party's rights.