Source : Webster's Revised Unabridged Dictionary (1913)

Ruler \Rul"er\ (r[udd]l"[~e]r), n.
   1. One who rules; one who exercises sway or authority; a
      governor.

            And he made him ruler over all the land. --Gen. xli.
                                                  43.

            A prince and ruler of the land.       --Shak.

   2. A straight or curved strip of wood, metal, etc., with a
      smooth edge, used for guiding a pen or pencil in drawing
      lines. Cf. {Rule}, n., 7
      (a)

Source : WordNet®

ruler
     n 1: measuring stick consisting of a strip of wood or metal or
          plastic with a straight edge that is used for drawing
          straight lines and measuring lengths [syn: {rule}]
     2: a person who rules or commands; "swayer of the universe"
        [syn: {swayer}]