The Collaborative International Dictionary of English v.0.48:

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]

WordNet (r) 3.0 (2006):

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

The Free On-line Dictionary of Computing (19 January 2023):

operator

    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)