The Collaborative International Dictionary of English v.0.48:

Govern \Gov"ern\, v. t. [imp. & p. p. Governed; p. pr. & vb.
   n. Governing.] [OF. governer, F. gouverner, fr. L.
   gubernare to steer, pilot, govern, Gr. kyberna^n. Cf.
   Gubernatorial.]
   1. To direct and control, as the actions or conduct of men,
      either by established laws or by arbitrary will; to
      regulate by authority. "Fit to govern and rule
      multitudes." --Shak.
      [1913 Webster]

   2. To regulate; to influence; to direct; to restrain; to
      manage; as, to govern the life; to govern a horse.
      [1913 Webster]

            Govern well thy appetite.             --Milton.
      [1913 Webster]

   3. (Gram.) To require to be in a particular case; as, a
      transitive verb governs a noun in the objective case; or
      to require (a particular case); as, a transitive verb
      governs the objective case.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Governing \Gov"ern*ing\, a.
   1. Holding the superiority; prevalent; controlling; as, a
      governing wind; a governing party in a state. --Jay.
      [1913 Webster]

   2. (Gram.) Requiring a particular case.
      [1913 Webster]

WordNet (r) 3.0 (2006):

governing
    adj 1: responsible for making and enforcing rules and laws;
           "governing bodies"
    n 1: the act of governing; exercising authority; "regulations
         for the governing of state prisons"; "he had considerable
         experience of government" [syn: government, governing,
         governance, government activity, administration]

Moby Thesaurus II by Grady Ward, 1.0:

73 Moby Thesaurus words for "governing":
   absolute, ascendant, at the head, authoritarian, authoritative,
   authorized, autocratic, boss, chief, clothed with authority,
   commanding, competent, consequential, considerable, controlling,
   directing, directive, directorial, directory, dominant,
   duly constituted, eminent, empowered, ex officio, general, great,
   guiding, head, hegemonic, hegemonistic, imperative, important,
   in ascendancy, in charge, in chief, in the ascendant, influential,
   leading, managerial, managing, master, mighty, momentous,
   monocratic, official, paramount, potent, powerful, predominant,
   predominate, preeminent, prepollent, preponderant, preponderate,
   prepotent, prestigious, prevalent, prominent, puissant, ranking,
   regnant, regulating, regulative, regulatory, reigning, ruling,
   senior, sovereign, substantial, superior, supreme, totalitarian,
   weighty