The Collaborative International Dictionary of English v.0.48:

Prescribe \Pre*scribe"\, v. i.
   1. To give directions; to dictate.
      [1913 Webster]

            A forwardness to prescribe to their opinions.
                                                  --Locke.
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   2. To influence by long use [Obs.] --Sir T. Browne.
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   3. (Med.) To write or to give medical directions; to indicate
      remedies; as, to prescribe for a patient in a fever.
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   4. (Law) To claim by prescription; to claim a title to a
      thing on the ground of immemorial use and enjoyment, that
      is, by a custom having the force of law.
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The Collaborative International Dictionary of English v.0.48:

Prescribe \Pre*scribe"\, v. t. [imp. & p. p. Prescribed; p. pr
   & vb. n. Prescribing.] [L. praescribere, praescriptum; prae
   before + scriebe to write. See Scribe.]
   [1913 Webster]
   1. To lay down authoritatively as a guide, direction, or rule
      of action; to impose as a peremptory order; to dictate; to
      appoint; to direct.
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            Prescribe not us our duties.          --Shak.
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            Let streams prescribe their fountains where to run.
                                                  --Dryden.
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   2. (Med.) To direct, as a remedy to be used by a patient; as,
      the doctor prescribed quinine.
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   Syn: To appoint; order; command; dictate; ordain; institute;
        establish.
        [1913 Webster]

WordNet (r) 3.0 (2006):

prescribe
    v 1: issue commands or orders for [syn: order, prescribe,
         dictate]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "prescribe":
   administer, advise, advocate, apply, appoint, assign, authorize,
   be responsible for, bestow, brief, call the signals, captain,
   carry on, choose, coach, command, conduct, confer, constitute,
   constrain, consult with, control, counsel, cure, decide,
   declare lawful, decree, define, demand, determine, dictate, direct,
   dose, dose with, enact, enforce upon, engineer, enjoin, establish,
   exact, fix, force, force upon, formulate, give, govern, guide,
   handle, head, head up, impose, instruct, kibitz, lay down, lay on,
   lead, lead on, legalize, legislate, legitimate, legitimatize,
   legitimize, make a regulation, make legal, make obligatory,
   make the rules, manage, maneuver, manipulate, mastermind, meddle,
   mete out to, officer, ordain, order, pick out, prescribe for,
   propose, pull the strings, put in force, put on, put upon,
   quarterback, recommend, regulate, remedy, require, rule, run,
   sanction, select, set, set down, settle, skipper, specify,
   stipulate, submit, suggest, take command, take the lead, treat,
   validate