A court order which prohibits a party from taking a particular course of action, such as picketing in the case of a union on strike.
Source: U.S. Department of Labor
A court order preventing one or more named parties from taking some action. A preliminary injunction often is issued to allow fact-finding, so a judge can determine whether a permanent injunction is justified.
Source: U.S. Courts
A court order that says a defendant can't perform, or must perform, a specific act. (Compare enjoin, restraining order.)
Source: California Courts.