The Collaborative International Dictionary of English v.0.48:

Proscribe \Pro*scribe"\, v. t. [imp. & p. p. Proscribed; p.
   pr. & vb. n. Proscribing.] [L. proscribere, proscriptum, to
   write before, to publish, proscribe; pro before + scribere to
   write. See Scribe. The sense of this word originated in the
   Roman practice of writing the names of persons doomed to
   death, and posting the list in public.]
   1. To doom to destruction; to put out of the protection of
      law; to outlaw; to exile; as, Sylla and Marius proscribed
      each other's adherents.
      [1913 Webster]

            Robert Vere, Earl of Oxford, . . . was banished the
            realm, and proscribed.                --Spenser.
      [1913 Webster]

   2. To denounce and condemn; to interdict; to prohibit; as,
      the Puritans proscribed theaters.
      [1913 Webster]

            The Arian doctrines were proscribed and
            anathematized in the famous Council of Nice.
                                                  --Waterland.
      [1913 Webster]

WordNet (r) 3.0 (2006):

proscribe
    v 1: command against; "I forbid you to call me late at night";
         "Mother vetoed the trip to the chocolate store"; "Dad nixed
         our plans" [syn: forbid, prohibit, interdict,
         proscribe, veto, disallow, nix] [ant: allow,
         countenance, let, permit]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "proscribe":
   anathematize, attaint, ban, banish, bar, blackball, blacklist,
   boycott, bring home to, cast out, censure, condemn, convict, cut,
   damn, debar, denounce, denunciate, deny, deport, disallow,
   disfellowship, doom, embargo, enjoin, exclude, exclude from,
   excommunicate, exile, expatriate, expel, extradite, find guilty,
   forbid, fugitate, inhibit, interdict, ostracize, outlaw,
   pass sentence on, penalize, preclude, prevent, prohibit,
   pronounce judgment, pronounce sentence, refuse, reject, relegate,
   repress, rule out, rusticate, say no to, send away, send down,
   send to Coventry, sentence, shut out, snub, spurn, suppress, taboo,
   thrust out, transport