noun (n)

• a person who is pursuing and trying to overtake or capture(noun.person)

  Example:
  Always before he had been able to outwit his pursuers.
  

  Synonym:
  chaser
  

  source: wordnet30
• a person who pursues some plan or goal(noun.person)

  Example:
  A pursuer of truth.
  

  source: wordnet30
• One who pursues or chases; one who follows in haste, with a view to overtake.(noun)

  source: webster1913