What is Petition?

Legal Definition
A petition is a request to do something, most commonly addressed to a government official or public entity. Petitions to a deity are a form of prayer called supplication.

In the colloquial sense, a petition is a document addressed to some official and signed by numerous individuals. A petition may be oral rather than written, and in this era may be transmitted via the Internet.
-- Wikipedia
Legal Definition
A formal application in writing made to a court or other official body requesting judicial action of some character.
Legal Definition
An instrument of writing or printing containing a prayer from the person presenting it, called the petitioner, to the body or person to whom it is presented, for the redress of some wrong, or the grant of some favor, which the latter has the right to give.

2. By the constitution of the United States the right "to petition the government for a redress of grievances," is secured to the people. Amendm. Art. 1.

3. Petitions are frequently presented to the courts in order to bring some matters before them. It is a general rule, in such cases, that an affidavit should be made that the facts therein contained are true as far as known to the petitioner, and that those facts which he states as knowing from others be believes to be true.
-- Bouviers Law Dictionary
Legal Definition
A written address, embodying an application or prayer from the person or persons preferring it, to the power, body or person to whom it is presented, for the exercise of his or their authority in the redress of some wrong or the grant of some favor, privilege or license. In practice. An application made to a court ex parte, or where there are no parties in opposition, praying for the exercise of the judicial powers of the' court in relation to some matter which is not the subject for a suit or action, or for authority to do some act which requires the sanction of the court; as for the appointment of a guardian, for leave to sell trust property, etc. The word "petition" is generally used in judicial proceedings to describe an application in writing, in contradistinction to a motion, which may be vivo voce. Bergen v. Jones, 4 Mete. (Mass.) 371. In the practice of some of the states, the word "petition" is adopted as the name of that initiatory pleading in an action which is elsewhere called a "declaration" or "complaint." See Code Ga. 1882, ยง 6332. In equity practice. An application in writing for an order of the court, stating the circumstances upon which it is founded; a proceeding resorted to whenever the nature of the application to the court requires a fuller statement than can be conveniently made in a notice of motion. 1 Barb. Ch. Pr. 578.
See also
-- Black's Law Dictionary
Legal Definition
A written request; a written application to a court. See 67 N. Y. 544, 23 Am. Rep. 138.
-- Ballentine's Law Dictionary