petitioner (n.)

• accuser
• adorer
• appellant
• applicant
• asker
• aspirant
• beadsman
• beggar
• bidder
• candidate
• celebrant
• chapelgoer
• churchgoer
• claimant
• communicant
• complainant
• congregation
• evangelist
• idolater
• informer
• party
• plaintiff
• postulant
• prayer
• prosecutor
• revivalist
• seeker
• solicitor
• suitor
• suppliant
• supplicant
• venerator
• votary
• worshiper