Rul"er (rûl"ẽr), 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.

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).

Parallel ruler. See under Parallel.