ruler

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One, such as a monarch or dictator, that rules or governs.
2. n. A straightedged strip, as of wood or metal, for drawing straight lines and measuring lengths. Also called rule.

Century Dictionary and Cyclopedia

1. n. One who rules or governs; one who exercises dominion or controlling power over others; a person who commands, manages, restrains, or has part in the making or administration of law; one in authority.
2. n. A rule; an instrument made of wood, brass, ivory, or the like, with straight edges or sides, by means of which, as a guide, straight lines may be drawn on paper, parchment, or other substance, by passing a pen or pencil along the edge. (See rule, and parallel ruler, under parallel.) When a ruler has the lines of chords, tangents, sines, etc., it is called a scale. See scale.
3. n. In engraving, a workman who operates a ruling-machine for ruling in flat tints, etc. See ruling-machine.
4. n. In line-engraving, a straight steel bar supported on cleats, to which a socket is so fitted that it slides evenly and steadily backward and forward. A perpendicular tube fixed to the side of the socket holds a sharp diamond-pointed graver which is pressed down by a spring. When the socket is drawn along the bar, the graver cuts a straight line across the plate; but by a slight motion of the hand lines can be formed to suit the shape of any object.

Wiktionary

1. n. A (usually rigid), flat, rectangular measuring or drawing device with graduations in units of measurement; a rule; a straightedge with markings; a measure.
2. n. A person who rules or governs; a person who exercises dominion or controlling power over others.

GNU Webster's 1913

1. n. One who rules; one who exercises sway or authority; a governor.
2. n. 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).

WordNet 3.0

1. n. a person who rules or commands
2. n. 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