noun (n)

• one praying humbly for something(noun.person)

  Synonym:
  requester, suppliant, supplicant
  

  source: wordnet30
• someone who petitions a court for redress of a grievance or recovery of a right(noun.person)

  Synonym:
  suer
  

  source: wordnet30
• One who presents a petition.(noun)

  source: webster1913