operator

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

• noun One who operates a machine or device.
• noun The owner or manager of a business.
• noun A military person who executes a special operation.
• noun Informal A person who is adept at accomplishing goals through shrewd or unscrupulous maneuvers.
• noun Mathematics A function, especially one from a set to itself, such as differentiation of a differentiable function or rotation of a vector.
• noun A logical operator.
• noun Genetics A chromosomal segment of DNA that regulates the activity of the structural genes of an operon by interacting with a specific repressor.

from The Century Dictionary.

• noun One who conducts a business, as mining; a capitalist who carries on a business: opposed to operative.
• noun One who operates in any way, or on or against anything.
• noun One who performs a surgical operation.
• noun One who exercises power, labor, skill, or influence in the accomplishment of some end; one who manipulates something, or is engaged in carrying on a series of acts or transactions by which some intended result is to be reached: as, a telegraph-operator; a Wall-street operator; an operator in wheat.
• noun In mathematics, a letter or other character signifying an operation to be performed, and itself subject to algebraical operation: as, a vector operator.
• noun where x, y, z are the rectangular coördinates of the variable point in space where the operand is found, and i, j, k are unit vectors respectively parallel to x, y, z.

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

• noun One who, or that which, operates or produces an effect.
• noun (Surg.) One who performs some act upon the human body by means of the hand, or with instruments.
• noun Brokers' Cant A dealer in stocks or any commodity for speculative purposes; a speculator.
• noun (Math.) The symbol that expresses the operation to be performed; -- called also facient.
• noun A person who operates a telephone switchboard.
• noun A person who schemes and maneuvers adroitly or deviously to achieve his/her purposes.

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

• noun One who operates.
• noun A telecommunications facilitator whose job is to establish temporary network connections.
• noun mathematics A function or other mapping that carries variables defined on a domain into another variable or set of variables in a defined range.
• noun Another name for Chinese whispers.
• noun informal A person who is adept at making deals or getting results, especially one who uses questionable methods.
• noun A member of a military Special Operations unit.
• noun computing The administrator of a channel or network on IRC.

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

• noun an agent that operates some apparatus or machine
• noun a speculator who trades aggressively on stock or commodity markets
• noun a shrewd or unscrupulous person who knows how to circumvent difficulties
• noun (mathematics) a symbol or function representing a mathematical operation
• noun someone who owns or operates a business