Synonyms for Supplication (same or very similar meaning)
WordNet sense 1 (a prayer asking God's help as part of a religious service):
invocationWordNet sense 2 (a humble request for help from someone in authority):
pleaWordNet sense 3 (the act of communicating with a deity (especially as a petition or in adoration or contrition or thanksgiving)):
prayer, prayerFrom the ODE community, based on WordNetadd/edit