The Collaborative International Dictionary of English v.0.48:

Injunction \In*junc"tion\, n. [L. injunctio, fr. injungere,
   injunctum, to join into, to enjoin. See Enjoin.]
   1. The act of enjoining; the act of directing, commanding, or
      prohibiting.
      [1913 Webster]

   2. That which is enjoined; an order; a mandate; a decree; a
      command; a precept; a direction.
      [1913 Webster]

            For still they knew, and ought to have still
            remembered,
            The high injunction, not to taste that fruit.
                                                  --Milton.
      [1913 Webster]

            Necessary as the injunctions of lawful authority.
                                                  --South.
      [1913 Webster]

   3. (Law) A writ or process, granted by a court of equity,
      and, in some cases, under statutes, by a court of law,
      whereby a party is required to do or to refrain from doing
      certain acts, according to the exigency of the writ.
      [1913 Webster]

   Note: It is more generally used as a preventive than as a
         restorative process, although by no means confined to
         the former. --Wharton. --Daniell. --Story.
         [1913 Webster]

WordNet (r) 3.0 (2006):

injunction
    n 1: a formal command or admonition
    2: (law) a judicial remedy issued in order to prohibit a party
       from doing or continuing to do a certain activity;
       "injunction were formerly obtained by writ but now by a
       judicial order" [syn: injunction, enjoining,
       enjoinment, cease and desist order]