The Collaborative International Dictionary of English v.0.48:

Restraint \Re*straint"\, n. [OF. restraincte, fr. restrainct, F.
   restreint, p. p. of restraindre, restrendre. See Restrain.]
   1. The act or process of restraining, or of holding back or
      hindering from motion or action, in any manner; hindrance
      of the will, or of any action, physical or mental.
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            No man was altogether above the restrains of law,
            and no man altogether below its protection.
                                                  --Macaulay.
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   2. The state of being restrained.
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   3. That which restrains, as a law, a prohibition, or the
      like; limitation; restriction.
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            For one restraint, lords of the world besides.
                                                  --Milton.
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   Syn: Repression; hindrance; check; stop; curb;?oercion;
        confinement; limitation; restriction.
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WordNet (r) 3.0 (2006):

restraint
    n 1: the act of controlling by restraining someone or something;
         "the unlawful restraint of trade"
    2: discipline in personal and social activities; "he was a model
       of polite restraint"; "she never lost control of herself"
       [syn: restraint, control] [ant: unrestraint]
    3: the state of being physically constrained; "dogs should be
       kept under restraint" [syn: constraint, restraint]
    4: a rule or condition that limits freedom; "legal restraints";
       "restraints imposed on imports"
    5: lack of ornamentation; "the room was simply decorated with
       great restraint" [syn: chasteness, restraint,
       simplicity, simpleness]
    6: a device that retards something's motion; "the car did not
       have proper restraints fitted" [syn: restraint,
       constraint]