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]

Moby Thesaurus II by Grady Ward, 1.0:

119 Moby Thesaurus words for "injunction":
   Eighteenth Amendment, Prohibition Party, Volstead Act, admonition,
   arrest, arrestation, ban, bar, barring, behest, bench warrant,
   bidding, blockade, boycott, capias, caveat, charge, check,
   circumscription, command, commission, constraint, contraband,
   control, cooling, cooling down, cooling off, curb, curtailment,
   death warrant, debarment, debarring, deceleration, demarcation,
   denial, dictate, direction, directive, disallowance, embargo,
   exception, exclusion, exhortation, fieri facias, forbiddance,
   forbidden fruit, forbidding, habere facias possessionem, hindrance,
   inadmissibility, index, index expurgatorius,
   index librorum prohibitorum, inhibition, instruction, interdict,
   interdiction, interdictum, law, legal restraint, lockout, mandamus,
   mandate, mandatory injunction, mittimus, monopoly, narrowing,
   nisi prius, no-no, nonadmission, notice, notification, omission,
   order, precept, preclusion, prescript, prescription, prevention,
   process, prohibition, prohibitory injunction, proscription,
   protection, protectionism, protective tariff, rationing, refusal,
   rein, rejection, relegation, repression, repudiation, restraint,
   restraint of trade, restriction, restrictive covenants,
   retardation, retrenchment, ruling, ruling out, search warrant,
   self-control, slowing down, statute, sumptuary laws, suppression,
   taboo, tariff wall, teaching, thought control, warning, warrant,
   warrant of arrest, warrant of attorney, word, writ, zoning,
   zoning laws



Bouvier's Law Dictionary, Revised 6th Ed (1856):

INJUNCTION, remedies, chancery, practice. An injunction is a prohibitory
writ, specially prayed for by a bill, in which the plaintiff's title is set
forth, restraining a person from committing or doing an act (other than
criminal acts) which appear to be against equity and conscience. Mitf. Pl.
124; 1 Madd. Ch. Pr. 126.
     2. Injunctions are of two kinds, the one called the writ remedial, and
the other the judicial writ.
     3.-1st. The former kind of injunction, or remedial writ, is in the
nature of a prohibition, directed to, and controlling, not the inferior
court, but the party. It is granted, when a party is doing or is about to do
an act against equity or good conscience, or litigious or vexatious; in
these cases, the court will not leave the party to feel the mischief or
inconvenience of the wrong, and look to the courts of common law for
redress, but will interpose its authority to restrain such unjustifiable
proceedings.
     4. Remedial injunctions are of two kinds common or special. 1. It is
common when it prays to stay proceedings at law, and will be granted, of
course; as, upon an attachment for want of an appearance, or of an answer;
or upon a dedimus obtained by the defendant to take his answer in the
country; or upon his praying for time to answer, &c. Newl. Pr. 92; 13 Ves,
323. 2. A special injunction is obtained only on motion or petition, with
notice to the other party, and is applied for, sometimes on affidavit before
answer, but more frequently upon the merits disclosed in the defendant's
answer. Injunctions before answer are granted in cases of waste and other
injuries of so urgent a nature, that mischief would ensue if the plaintiff
were to wait until the answer were put in; but the court will not grant an
injunction during the pendency of a plea or demurrer to the bill, for until
that be argued, it does not appear whether or not the court has jurisdiction
of the cause. The injunction granted in this stage of the suit, is to
continue till answer or further order; the injunction obtained upon the
merits confessed in the answer, continues generally till the hearing of the
cause.
     5. An injunction is generally granted for the purpose of preventing a
wrong, or preserving property in dispute pending a suit. Its effect, in
general, is only in personam, that is, to attach and punish the party if
disobedient in violating the injunction. Ed. Inj. 363; Harr. Ch. Pr. 552.
     6. The principal injuries which may be prevented by injunction, relate
to the person, to personal property, or to real property. These will be
separately considered.
     7.-1. With respect to the person, the chancellor may prevent a breach
of the peace, by requiring sureties of the peace. A court of chancery has
also summary and extensive jurisdiction for the protection of the relative
rights of persons, as between husband and wife, parent and child, and
guardian and ward; and in these cases, on a proper state of facts, an
injunction will be granted. For example, an injunction may be obtained by a
parent to prevent the marriage of his infant son. 1 Madd. Ch. Pr. 348; Ed.
Inj. 297; 14 Ves. 206; 19 Ves. 282; 1 Chitty. Pr. 702.
     8.-2. Injunctions respecting personal property, are usually granted,
1st. To restrain a partner or agent from making or negotiating bills, notes
or contracts, or doing other acts injurious to the partner or principal. 3
Ves. jr. 74; 3 Bro. C. C. 15; 2 Campb. 619; 1 Price, R. 503; 1 Mont. on
Part. 93; 1 Madd. Ch. Pr. 160; Chit. Bills, 58, 61; 1 Hov. Supp. to Ves. jr.
335; Woodes. Lect. 416.
     9.-2d. To restrain the negotiation of bills or notes obtained by
fraud, or without consideration. 8 Price, R. 631; Chit. Bills, 31 to 41; Ed.
Inj. 210; Blake's Ch. Pr. 838; 2 Anst. 519; 3 Anst. 851; 2 Ves. jr. 493; 1
Fonb. Eq. 43; 1 Madd. Ch. Pr. 154. 3d. To deliver up void or satisfied
deeds. 1 V. & B. 244; 11 Ves. 535; 17 Ves. 111. 4th. To enter into and
deliver a proper security. 1 Anst, 49. 5th. To prevent breaches of covenant
or contract, and enjoin the performance of others. Ed. Inj. 308. 6th. To
prevent a breach of confidence or good faith, or to prevent other loss as,
for example, to restrain the disclosure of secrets, which came to the
defendant's knowledge in the course of any confidential employment. 1 Sim.
R. 483 and see 1 Jac. & W. 394. An injunction will be granted to prevent the
publication of private letters without the authors consent. Curt. on Copyr.
90; 2 Atk. 342; Ambl. 137; 2 Swanst. 402, 427; 1 Ball & Beat. 207; 2 Ves. &
B. 19; 1 Mart. Lo. R. 297; Bac. Ab. Injunction A. But the publication will
be allowed when necessary to the defence of the character of the party who
received them. 2 Ves. & B. 19. 7th. To prevent improper sales, payments, or
conveyances. Chit. Eq. Dig. tit. Practice, xlvii. 8th. To prevent loss or
inconvenience; this can be obtained on filing a bill quia timet. (q. v.) 1
Madd. Ch. Pr. 218 to 225. 9th. To prevent waste of property by an executor
or administrator. Ed. Inj. 300; 1 Madd. Ch. Pr.; 160, 224. 10th. To restrain
the infringement of patents; Ed. Inj. ch. 12; 14 Ves. 130; 1 Madd. Ch. Pr.
137; or of copyrights; Ed. Inj. c. 13; 8 Ares. 225; 17 Ves. 424. 11th. To
stay proceedings in a court of law. These proceedings will be stayed when
justice cannot be done in consequence of accident; 1 John. Cas. 417: 4 John.
Ch. R. 287,194; Latch, 24, 146, 148; 1 Vern. 180, 247; 1 Ch. C. 77, 120; 1
Eq. Cas. Ab. 92; or mistake; 1 John. Ch. R. 119, 607; 2 John. Ch. R. 585; 4
John. Ch. R. 85; Id. 144; 2 Munf. 187; 1 Day's Cas. Err. 139; 3 Ch. R. 55;
Finch., 413; 2 Freem. 16; Fitzg. 118; or fraud. 1 John. Ch. R. 402; 2 John.
Ch. R. 512; 4 John. Ch. R. 65. But no injunction will be granted to stay
proceedings in a criminal case. 2 John. Ch. R. 387; 6 Mod. 12; 2 Ves. 396.
     9.-3. Injunctions respecting real property, may be obtained, 1st. To
prevent wasteful trespasses or irreparable damages, although the owner may
be entitled to retake possession, if he can do so, without a breach of the
peace. 1 Chit. Pr. 722. 2d. To compel the performance of lawful works in the
least, injurious manner. 1 Turn. & Myl. 181. 3d. To prevent waste. 3 Tho.
Co. Litt. 241, M; 1 Madd. Ch. Pr. 138; Ed. Inj. ch. 8, 9, and 10; 1 John.
Ch. R. 11; 2 Atk. 183. 4th. To prevent the creation of a nuisance, either
private or public. 1. Private nuisance; for example, to restrain the owner
of a house from making any erections or improvements, so as materially to
darken or obstruct the ancient lights and windows of an adjoining house. 2
Russ. R. 121. 2. Public nuisances. Though usual to prosecute the parties who
create nuisances, by indictment, yet, in some cases, an injunction may be
had to prevent the creating of such nuisance. 5 Ves. 129; 1 Mad. Ch. 156;
Ed. Inj. ch. 11.
    10.-2d An injunction of the second kind, called the judicial writ,
issues subsequently to a decree. It is a direction to yield up, to quit, or
to continue possession of lands, and is properly described as being in the
nature of an execution. Ed. Inj. 2.
    11. Injunctions are also divided into temporary and perpetual. 1. A
temporary injunction is one which is granted until some stage of the suit
shall be reached; as, until the defendant shall file his answer; until the
bearing; and the like. 2. A perpetual injunction is one which is issued
when, in the opinion of the court, at the hearing the plaintiff has
established a case, which entitles him to an injunction; or when a bill,
praying for an injunction, is taken pro confesso; in such cases a perpetual
injunction will be decreed. Ed. Inj. 253.
    12. The interdict (q. v.) of the Roman law resembles, in many respects,
our injunction. It was used in three distinct, but cognate senses. 1. It was
applied to signify the edicts made by the proctor, declaratory of his
intention to give a remedy in certain cases, chiefly to preserve or to
restore possession; this interdict was called edictal; edictale, quod
praetoriis edictis proponitur, ut sciant omnes ea forma posse implorari. 2.
It was used to signify his order or decree, applying the remedy in the given
case before him, and then was called decretal; decretale, quod praetor re
nata implorantibus decrevit. It is this which bears a strong resemblance to
the injunction of a court of equity. 3. It was used, in the last place, to
signify the very remedy sought in the suit commenced under the proctor's
edict; and thus it became the denomination of the action itself. Livingston
on the Batture case, 5, Am. Law Jour. 271; 2 Story, Eq. Jur. Sec. 865;
Analyse des Pandectes de Pothier, h.t.; Dict. du Dig. h.t.; Clef des Lois
Rom. h. t.; Heineccii, Elem. Pand.  Ps. 6, Sec. 285, 28
     Vide, generally, Eden on Injunctions; 1 Madd. Ch. Pr. 125 to 165;
Blake's Ch. Pr. 330 to 344; 1 Chit. Pr. 701 to 731; Coop. Eq. Pl. Index, h.
t.; Redesd. Pl. Index, h. t.; Smith's Ch. Pr. h. t.; 14 Vin. Ab. 442; 2 Hov.
Supp. to Ves. jr. 173, 434, 442; Com. Dig. Chancery, D 8; Newl. Pr. o. 4, s.
7; Bouv. Inst. Index, h. t.