The Collaborative International Dictionary of English v.0.48:

petitio \petitio\ n. (Rhetoric, Logic)
   The fallacy of assuming the conclusion in the premises;
   begging the question.

   Syn: petitio principii.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

petitio
    n 1: the logical fallacy of assuming the conclusion in the
         premises; begging the question [syn: petitio principii,
         petitio]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

PETITION. 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. Amend.
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.