The Collaborative International Dictionary of English v.0.48:

Impose \Im*pose"\, v. t. [imp. & p. p. Imposed; p. pr. & vb.
   n. Imposing.] [F. imposer; pref. im- in + poser to place.
   See Pose, v. t.]
   1. To lay on; to set or place; to put; to deposit.
      [1913 Webster]

            Cakes of salt and barley [she] did impose
            Within a wicker basket.               --Chapman.
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   2. To lay as a charge, burden, tax, duty, obligation,
      command, penalty, etc.; to enjoin; to levy; to inflict;
      as, to impose a toll or tribute.
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            What fates impose, that men must needs abide.
                                                  --Shak.
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            Death is the penalty imposed.         --Milton.
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            Thou on the deep imposest nobler laws. --Waller.
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   3. (Eccl.) To lay on, as the hands, in the religious rites of
      confirmation and ordination.
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   4. (Print.) To arrange in proper order on a table of stone or
      metal and lock up in a chase for printing; -- said of
      columns or pages of type, forms, etc.
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The Collaborative International Dictionary of English v.0.48:

imposed \imposed\ adj.
   p. p. of impose; as, rules imposed by society.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

imposed
    adj 1: set forth authoritatively as obligatory; "the imposed
           taxation"; "rules imposed by society"

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "imposed":
   absolute, binding, compulsory, conclusive, decisive, decretory,
   dictated, entailed, final, hard-and-fast, imperative, irrevocable,
   mandated, mandatory, must, obligatory, peremptory, prescript,
   prescriptive, required, ultimate, without appeal