noun (n)

• (mathematics) a symbol or function representing a mathematical operation(noun.linkdef)

  source: wordnet30
• an agent that operates some apparatus or machine(noun.person)

  Example:
  The operator of the switchboard.
  

  Synonym:
  manipulator
  

  source: wordnet30
• someone who owns or operates a business(noun.person)

  Example:
  Who is the operator of this franchise?.
  

  source: wordnet30
• a shrewd or unscrupulous person who knows how to circumvent difficulties(noun.person)

  Synonym:
  hustler, wheeler dealer
  

  source: wordnet30
• a speculator who trades aggressively on stock or commodity markets(noun.person)

  source: wordnet30
• One who, or that which, operates or produces an effect.(noun)

  source: webster1913