1.A prayer; a supplication; an imploration; an entreaty; especially, a request of a solemn or formal kind; a prayer to the Supreme Being, or to a person of superior power, rank, or authority; also, a single clause in such a prayer. "A house of prayer and petition for thy people." "This last petition heard of all her prayer."
2.A formal written request addressed to an official person, or to an organized body, having power to grant it.
3.Specifically: (Law), A request to government, in either of its branches, for the granting of a particular grace or right, or for the legislature to take a specific action; in distinction from a memorial, which calls certain facts to mind. The petition may be signed by one or any number of persons.