From The Collaborative International Dictionary of English v.0.48 [gcide]:
Operator \Op"er*a`tor\, n. [L.]
1. One who, or that which, operates or produces an effect.
[1913 Webster]
2. (Surg.) One who performs some act upon the human body by
means of the hand, or with instruments.
[1913 Webster]
3. A dealer in stocks or any commodity for speculative
purposes; a speculator. [Brokers' Cant]
[1913 Webster]
4. (Math.) The symbol that expresses the operation to be
performed; -- called also facient.
[1913 Webster]
5. A person who operates a telephone switchboard.
[PJC]
6. A person who schemes and maneuvers adroitly or deviously
to achieve his/her purposes.
[PJC]
From WordNet (r) 3.0 (2006) [wn]:
operator
n 1: (mathematics) a symbol or function representing a
mathematical operation
2: an agent that operates some apparatus or machine; "the
operator of the switchboard" [syn: operator, manipulator]
3: someone who owns or operates a business; "who is the operator
of this franchise?"
4: a shrewd or unscrupulous person who knows how to circumvent
difficulties [syn: hustler, wheeler dealer, operator]
5: a speculator who trades aggressively on stock or commodity
markets
From The Free On-line Dictionary of Computing (8 July 2008) [foldoc]:
operator
<programming> A symbol used as a function, with {infix
syntax} if it has two arguments (e.g. "+") or prefix syntax if
it has only one (e.g. Boolean NOT). Many languages use
operators for built-in functions such as arithmetic and logic.
(1995-04-30)