The Collaborative International Dictionary of English v.0.48:

Parson \Par"son\, n. [OE. persone person, parson, OF. persone,
   F. personne person, LL. persona (sc. ecclesiae), fr. L.
   persona a person. See Person.]
   [1913 Webster]
   1. (Eng. Eccl. Law) A person who represents a parish in its
      ecclesiastical and corporate capacities; hence, the rector
      or incumbent of a parochial church, who has full
      possession of all the rights thereof, with the cure of
      souls.
      [1913 Webster]

   2. Any clergyman having ecclesiastical preferment; one who is
      in orders, or is licensed to preach; a preacher.
      [1913 Webster]

            He hears the parson pray and preach.  --Longfellow.
      [1913 Webster]

   Parson bird (Zool.), a New Zealand bird (Prosthemadera
      Nov[ae]seelandi[ae]) remarkable for its powers of mimicry
      and its ability to articulate words. Its color is glossy
      black, with a curious tuft of long, curly, white feathers
      on each side of the throat. It is often kept as a cage
      bird.
      [1913 Webster]

WordNet (r) 3.0 (2006):

parson
    n 1: a person authorized to conduct religious worship;
         "clergymen are usually called ministers in Protestant
         churches" [syn: curate, minister of religion,
         minister, parson, pastor, rector]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "parson":
   DD, Doctor of Divinity, Holy Joe, abbe, chaplain, churchman,
   clergyman, cleric, clerical, clerk, curate, cure, divine,
   ecclesiastic, man of God, military chaplain, minister, padre,
   pastor, rector, reverend, servant of God, shepherd, sky pilot,
   supply clergy, supply minister, the Reverend, the very Reverend,
   tonsured cleric



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

PARSON, eccl. law. One who has full possession of all the rights of a
parochial church.
     2. He is so called because by his person the church, which is an
invisible body, is represented: in England he is himself a body corporate it
order to protect and defend the church (which he personates) by a the
minority, if required to bring Story on Partn. Sec. 489. 1 Bouv. Inst. n.
1217. 398; 5 Com. Dig. 346.