ˈrülə(r) noun
( -s )
Etymology: Middle English reuler, from reulen to rule + -er — more at rule
1.
a. : one that exercises authority, command, or dominating influence
the old male was even in captivity the undisputed guardian and ruler of all the other members — Weston La Barre
the rulers of modern art
an ambition that became the ruler of his life
specifically : one who rules over a nation or people
an able and vigorous ruler who reunited his country
their position in our democratic system as the informants of our rulers, the people — F.L.Mott
b. : one who exercises control in some limited field
was the ruler of Admiralty Room 40 — British Book News
2. : one that rules lines: as
a. : a straight or curved strip (as of wood or metal) with a smooth edge usually marked off in units (as inches or centimeters) and used for guiding a pen or pencil in drawing lines or for measuring
b. : an operator of a machine for drawing ink lines on paper