English to English

noun (n)

• someone who deliberately foments trouble(noun.person)

  Example:
  She was the instigator of their quarrel.
  

  Synonym:
  firebrand, inciter, instigant, provoker
  

  source: wordnet30
• a person who initiates a course of action(noun.person)

  Synonym:
  initiator
  

  source: wordnet30
• One who instigates or incites.(noun)

  source: webster1913