n. (Rhetoric, Logic) The fallacy of assuming the conclusion in the premises; begging the question.
Syn. -- petitio principii. [ WordNet 1.5 ]

n. [ F. pétition, L. petitio, fr. petere, petitum, to beg, ask, seek; perh. akin to E. feather, or find. ] 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. [ 1913 Webster ]

A house of prayer and petition for thy people. 1 Macc. vii. 37. [ 1913 Webster ]

This last petition heard of all her prayer. Dryden. [ 1913 Webster ]

2. A formal written request addressed to an official person, or to an organized body, having power to grant it. [ 1913 Webster ]

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. [ 1913 Webster + PJC ]

4. The written document containing a petition (senses 1 or 2). [ 1913 Webster ]

Petition of right (Law), a petition to obtain possession or restitution of property, either real or personal, from the Crown, which suggests such a title as controverts the title of the Crown, grounded on facts disclosed in the petition itself. Mozley & W. --
The Petition of Right (Eng. Hist.), the parliamentary declaration of the rights of the people, assented to by Charles I. [ 1913 Webster ]

v. t. [ imp. & p. p. Petitioned p. pr. & vb. n. Petitioning. ] To make a prayer or request to; to ask from; to solicit; to entreat; especially, to make a formal written supplication, or application to, as to any branch of the government; as, to petition the court; to petition the governor. [ 1913 Webster ]

You have . . . petitioned all the gods for my prosperity. Shak. [ 1913 Webster ]

v. i. To make a petition or solicitation. [ 1913 Webster ]

adv. By way of begging the question; by an assumption. [ R. ] Sir T. Browne. [ 1913 Webster ]

a. 1. Supplicatory; making a petition. [ 1913 Webster ]

Pardon Rome, and any petitionary countrymen. Shak. [ 1913 Webster ]

2. Containing a petition; of the nature of a petition; as, a petitionary epistle. Swift. [ 1913 Webster ]

n. A person cited to answer, or defend against, a petition. [ 1913 Webster ]

n. One who presents a petition. [ 1913 Webster ]

n. The act of presenting apetition; a supplication. [ 1913 Webster ]