The Collaborative International Dictionary of English v.0.48:

Dictum \Dic"tum\, n.; pl. L. Dicta, E. Dictums. [L., neuter
   of dictus, p. p. of dicere to say. See Diction, and cf.
   Ditto.]
   1. An authoritative statement; a dogmatic saying; an
      apothegm.
      [1913 Webster]

            A class of critical dicta everywhere current. --M.
                                                  Arnold.
      [1913 Webster]

   2. (Law)
      (a) A judicial opinion expressed by judges on points that
          do not necessarily arise in the case, and are not
          involved in it.
      (b) (French Law) The report of a judgment made by one of
          the judges who has given it. --Bouvier.
      (c) An arbitrament or award.
          [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

162 Moby Thesaurus words for "dictum":
   Parthian shot, a priori truth, action, adage, address, affirmance,
   affirmation, allegation, ana, analects, announcement, annunciation,
   answer, aphorism, apostrophe, apothegm, appointment, assertion,
   asseveration, averment, avouchment, avowal, award, axiom, brevet,
   brocard, bull, byword, canon, catchword, code, collected sayings,
   commandment, comment, conclusion, condemnation, consideration,
   convention, crack, creed, current saying, decision, declaration,
   decree, decree-law, decreement, decretal, decretum, deliverance,
   determination, diagnosis, dictate, diktat, distich, doom, edict,
   edictum, enunciation, epigram, exclamation, expression, fiat,
   finding, form, formula, general principle, gnome, golden rule,
   golden saying, greeting, guideline, guiding principle, imperative,
   interjection, ipse dixit, law, manifesto, maxim, mention, mitzvah,
   moral, mot, motto, norm, note, observation, oracle, order,
   ordinance, ordonnance, phrase, pithy saying, position,
   position paper, positive declaration, postulate, precedent,
   precept, predicate, predication, prescript, principium, principle,
   proclamation, profession, prognosis, pronouncement, pronunciamento,
   proposition, protest, protestation, proverb, proverbial saying,
   proverbs, question, reflection, regulation, remark, rescript,
   resolution, rubric, rule, ruling, saw, say, say-so, saying,
   self-evident truth, senatus consult, senatus consultum, sentence,
   sententious expression, settled principle, sloka, stance, stand,
   standard, statement, stock saying, subjoinder, sutra, teaching,
   tenet, text, theorem, thought, truism, truth, ukase,
   universal truth, utterance, verdict, verse, vouch, wisdom,
   wisdom literature, wise saying, witticism, word, words of wisdom,
   working principle, working rule