The Collaborative International Dictionary of English v.0.48:

Ruling \Rul"ing\, a.
   1. Predominant; chief; reigning; controlling; as, a ruling
      passion; a ruling sovereign.
      [1913 Webster]

   2. Used in marking or engraving lines; as, a ruling machine
      or pen.
      [1913 Webster]

   Syn: Predominant; chief; controlling; directing; guiding;
        governing; prevailing; prevalent.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ruling \Rul"ing\, n.
   1. The act of one who rules; ruled lines.
      [1913 Webster]

   2. (Law) A decision or rule of a judge or a court, especially
      an oral decision, as in excluding evidence.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rule \Rule\, n.
   [Webster 1913 Suppl.]

   Syn: regulation; law; precept; maxim; guide; canon; order;
        method; direction; control; government; sway; empire.
        [1913 Webster] Rule \Rule\, v. t. [imp. & p. p. Ruled;
   p. pr. & vb. n. Ruling.] [Cf. OF. riuler, ruiler, L.
   regulare. See Rule, n., and cf. Regulate.]
   1. To control the will and actions of; to exercise authority
      or dominion over; to govern; to manage. --Chaucer.
      [1913 Webster]

            A bishop then must be blameless; . . . one that
            ruleth well his own house, having his children in
            subjection.                           --1 Tim. iii.
                                                  2, 4.
      [1913 Webster]

   2. To control or direct by influence, counsel, or persuasion;
      to guide; -- used chiefly in the passive.
      [1913 Webster]

            I think she will be ruled
            In all respects by me.                --Shak.
      [1913 Webster]

   3. To establish or settle by, or as by, a rule; to fix by
      universal or general consent, or by common practice.
      [1913 Webster]

            That's are ruled case with the schoolmen.
                                                  --Atterbury.
      [1913 Webster]

   4. (Law) To require or command by rule; to give as a
      direction or order of court.
      [1913 Webster]

   5. To mark with lines made with a pen, pencil, etc., guided
      by a rule or ruler; to print or mark with lines by means
      of a rule or other contrivance effecting a similar result;
      as, to rule a sheet of paper of a blank book.
      [1913 Webster]

   Ruled surface (Geom.), any surface that may be described by
      a straight line moving according to a given law; -- called
      also a scroll.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ruling
    adj 1: exercising power or authority [syn: regnant,
           reigning, ruling]
    n 1: the reason for a court's judgment (as opposed to the
         decision itself) [syn: opinion, ruling]

Moby Thesaurus II by Grady Ward, 1.0:

198 Moby Thesaurus words for "ruling":
   absolute, act, action, appointment, arch, armipotent, ascendant,
   at the head, authoritarian, authoritative, authorized, autocratic,
   average, award, banner, besetting, bill, boss, brevet, bull, bylaw,
   canon, capital, cardinal, central, champion, chief,
   clothed with authority, cogent, commanding, common, competent,
   condemnation, consequential, considerable, consideration,
   controlling, crowning, current, decision, declaration, decree,
   decree-law, decreement, decretal, decretum, deliverance,
   determination, diagnosis, dictate, dictation, dictum, diktat,
   directive, dominant, doom, duly constituted, dynamic, edict,
   edictum, effective, eminent, empowered, enactment, energetic,
   epidemic, ex officio, fiat, finding, first, focal, forceful,
   forcible, foremost, form, formality, formula, formulary, general,
   governing, great, head, headmost, hegemonic, hegemonistic,
   high-potency, high-powered, high-pressure, high-tension,
   imperative, important, in ascendancy, in charge, in chief,
   in force, in power, in the ascendant, influential, institution,
   ipse dixit, irresistible, jus, law, leading, legislation, lex,
   magisterial, main, master, measure, mighty, mighty in battle,
   momentous, monocratic, normal, official, on the throne, operative,
   order, ordinance, ordinary, ordonnance, overriding, overruling,
   pandemic, paramount, pivotal, popular, potent, powerful, precedent,
   predominant, predominate, predominating, preeminent, prepollent,
   preponderant, preponderate, prepotent, prescript, prescription,
   prestigious, prevailing, prevalent, primal, primary, prime,
   principal, proclamation, prognosis, prominent, pronouncement,
   pronunciamento, puissant, rampant, ranking, regnant, regulating,
   regulation, regulative, regulatory, reigning, rescript, resolution,
   rife, routine, rubric, rule, running, senatus consult,
   senatus consultum, senior, sentence, sovereign, standard,
   standing order, star, statute, stellar, stereotyped, striking,
   strong, substantial, supereminent, superior, supreme, swaying,
   telling, topflight, totalitarian, ukase, usual, valid, verdict,
   vigorous, vital, weighty, widespread