Source : Webster's Revised Unabridged Dictionary (1913)

Reign \Reign\ (r?n), v. i. [imp. & p. p. {Reigned} (r?nd); p.
   pr. & vb. n. {Reigning}.] [OE. regnen, reinen, OF. regner, F.
   r['e]gner, fr. L. regnare, fr. regnum. See {Reign}, n.]
   1. To possess or exercise sovereign power or authority; to
      exercise government, as a king or emperor;; to hold
      supreme power; to rule. --Chaucer.

            We will not have this man to reign over us. --Luke
                                                  xix. 14.

            Shall Banquo's issue ever Reign in this kingdom?
                                                  --Shak.

   2. Hence, to be predominant; to prevail. ``Pestilent diseases
      which commonly reign in summer.'' --Bacon.

   3. To have superior or uncontrolled dominion; to rule.

            Let not sin therefore reign in your mortal body.
                                                  --Rom. vi. 12.

   Syn: To rule; govern; direct; control; prevail.

Source : WordNet®

reigning
     adj : exercising power or authority [syn: {regnant}, {ruling}]