regulator

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. One that regulates, as:
2. n. The mechanism in a watch by which its speed is governed.
3. n. A highly accurate clock used as a standard for timing other clocks.
4. n. A device used to maintain uniform speed in a machine; a governor.
5. n. A device used to control the flow of gases, liquids, or electric current.
6. n. One, such as the member of a governmental regulatory agency, that ensures compliance with laws, regulations, and established rules: banking regulators; price regulators.
7. n. A substance that affects the amount of product or the progress of a biochemical reaction or process: a regulator of embryogenesis.
8. n. See regulator gene.

Century Dictionary and Cyclopedia

1. n. One who or that which regulates. Members of the unauthorized associations which have at various times been formed in parts of the United States for the carrying out of a rough substitute for justice in the case of heinous or notorious crimes have been called regulators.
2. n. A mechanical contrivance intended to produce uniformity of motion, temperature, power, etc. In engineering and machinery: A governor in the sense described and illustrated under governor, 6.
3. n. The original valve-motion of Watt's double-action condensing pumping-engine. It was a valve-box having a spindle through one of its sides, on which was a toothed sector working on a central bearing, and meshing with a rack attached to a valve. A tripping-lever attached to the sector and operated by the plug-tree caused the oscillations of the latter to open and close the valve.

Wiktionary

1. n. A device that controls or limits something.
2. n. A person or group that sets standards of practice, especially those established by law.
3. n. A very accurate clock, used by clockmakers to measure the timekeeping of each newly made clock.

GNU Webster's 1913

1. n. One who, or that which, regulates.
2. n. (Mach.) A contrivance for regulating and controlling motion.
3. n. The lever or index in a watch, which controls the effective length of the hairspring, and thus regulates the vibrations of the balance.
4. n. The governor of a steam engine.
5. n. A valve for controlling the admission of steam to the steam chest, in a locomotive.
6. n. A clock, or other timepiece, used as a standard of correct time. See Astronomical clock (a), under Clock.
7. n. U.S. A member of a volunteer committee which, in default of the lawful authority, undertakes to preserve order and prevent crimes; also, sometimes, one of a band organized for the comission of violent crimes.

WordNet 3.0

1. n. any of various controls or devices for regulating or controlling fluid flow, pressure, temperature, etc.
2. n. a control that maintains a steady speed in a machine (as by controlling the supply of fuel)
3. n. an official responsible for control and supervision of a particular activity or area of public interest