The Collaborative International Dictionary of English v.0.48:

Ordain \Or*dain"\, v. t. [imp. & p. p. Ordained; p. pr. & vb.
   n. Ordaining.] [OE. ordeinen, OF. ordener, F. ordonner, fr.
   L. ordinare, from ordo, ordinis, order. See Order, and cf.
   Ordinance.]
   1. To set in order; to arrange according to rule; to
      regulate; to set; to establish. "Battle well ordained."
      --Spenser.
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            The stake that shall be ordained on either side.
                                                  --Chaucer.
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   2. To regulate, or establish, by appointment, decree, or law;
      to constitute; to decree; to appoint; to institute.
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            Jeroboam ordained a feast in the eighth month. --1
                                                  Kings xii. 32.
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            And doth the power that man adores ordain
            Their doom ?                          --Byron.
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   3. To set apart for an office; to appoint.
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            Being ordained his special governor.  --Shak.
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   4. (Eccl.) To invest with ministerial or sacerdotal
      functions; to introduce into the office of the Christian
      ministry, by the laying on of hands, or other forms; to
      set apart by the ceremony of ordination.
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            Meletius was ordained by Arian bishops. --Bp.
                                                  Stillingfleet.
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WordNet (r) 3.0 (2006):

ordain
    v 1: order by virtue of superior authority; decree; "The King
         ordained the persecution and expulsion of the Jews"; "the
         legislature enacted this law in 1985" [syn: ordain,
         enact]
    2: appoint to a clerical posts; "he was ordained in the Church"
       [syn: ordain, consecrate, ordinate, order]
    3: invest with ministerial or priestly authority; "The minister
       was ordained only last month"
    4: issue an order

Moby Thesaurus II by Grady Ward, 1.0:

116 Moby Thesaurus words for "ordain":
   allocate, allot, appoint, appropriate to, assign, assign to,
   authorize, bid, call on, call the signals, call upon, canonize,
   carry on, charge, command, commission, consecrate, constitute,
   declare, declare lawful, decree, designate, destinate, destine,
   detail, devote, dictate, direct, doom, earmark, enact, enact laws,
   enjoin, enlist, enroll, establish, fate, filibuster, foredoom,
   formulate, frock, get the floor, give an order, give the word,
   have the floor, impose, inaugurate, induct, initiate, install,
   instate, instruct, invest, issue a command, issue a writ, keep,
   kill, lay down, legalize, legislate, legitimate, legitimatize,
   legitimize, lobby through, logroll, lot, make a regulation,
   make assignments, make legal, manage, mandate, mark, mark off,
   mark out for, name, nominate, operate, order, order about,
   ordinate, pass, pigeonhole, pocket, portion off, prescribe,
   proclaim, promulgate, pronounce, put in force, put through,
   railroad through, regulate, reserve, restrict, restrict to,
   roll logs, rule, run, saint, sanction, say the word, schedule,
   select, set, set apart, set aside, set off, sign on, sign up, tab,
   table, tag, take the floor, validate, veto, yield the floor



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

ORDAIN. To ordain is to make an ordinance, to enact a law.
     2. In the constitution of the United States, the preamble. declares
that the people "do ordain and establish this constitution for the United
States of America." The 3d article of the same constitution declares, that
"the judicial power shall be vested in one supreme court, and in such
inferior courts as the congress may from time to time ordain and establish.
"See 1 Wheat. R. 304, 324; 4 Wheat: R. 316, 402.