controller

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One that controls.
• noun An officer who audits accounts and supervises the financial affairs of a corporation or of a governmental body.
• noun A regulating mechanism, as in a vehicle or electric device.

from The Century Dictionary.

• noun Specifically An officer who has certain duties to perform in examining the accounts and managing the financial affairs of a public or private corporation, or of a city, state, or government.
• noun In mech., a part of an apparatus or an adjunct which controls the motion or operation of the main part.
• noun In ship-building, a heavy iron block secured to the deck near a hawse-pipe, with a movable section so arranged that the chain cable passing over it is held or allowed to run out as the movable section is lowered or raised.
• noun 1. One who has charge of the receipt and expenditure of money.
• noun Specifically—2. An officer who has certain duties to perform in examining the accounts and managing the financial affairs of a public or private corporation, or of a city, state, or government.
• noun One who controls or restrains; one who has the power or authority to govern or control; one who governs or regulates.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who, or that which, controls or restraines; one who has power or authority to regulate or control; one who governs.
• noun An officer appointed to keep a counter register of accounts, or to examine, rectify, or verify accounts.
• noun (Naut.) An iron block, usually bolted to a ship's deck, for controlling the running out of a chain cable. The links of the cable tend to drop into hollows in the block, and thus hold fast until disengaged.
• noun (Elec.) Any electric device for controlling a circuit or system
• noun An electromagnet, excited by the main current, for throwing a regulator magnet into or out of circuit in an automatic device for constant current regulation.
• noun A kind of multiple switch for gradually admitting the current to, or shutting it off from, an electric motor.
• noun (Mach.) A lever controlling the speed of an engine; -- applied esp. to the lever governing a throttle valve, as of a steam or gasoline engine, esp. on an automobile.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One who controls something.
• noun A person who audits, and manages the financial affairs of a company or government; a comptroller.
• noun A mechanism that controls or regulates the operation of a machine, especially a peripheral device in a computer.
• noun nautical An iron block, usually bolted to a ship's deck, for controlling the running out of a chain cable. The links of the cable tend to drop into hollows in the block, and thus hold fast until disengaged.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a person who directs and restrains
• noun a mechanism that controls the operation of a machine
• noun someone who maintains and audits business accounts