The Collaborative International Dictionary of English v.0.48:

Patron \Pa"tron\, a.
   Doing the duty of a patron; giving aid or protection;
   tutelary. --Dryden.
   [1913 Webster]

   Patron saint (R. C. Ch.), a saint regarded as the peculiar
      protector of a country, community, church, profession,
      etc., or of an individual.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Patron \Pa"tron\, n. [F., fr. L. patronus, fr. pater a father.
   See Paternal, and cf. Patroon, Padrone, Pattern.]
   1. One who protects, supports, or countenances; a defender.
      "Patron of my life and liberty." --Shak. "The patron of
      true holiness." --Spenser.
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   2. (Rom. Antiq.)
      (a) A master who had freed his slave, but still retained
          some paternal rights over him.
      (b) A man of distinction under whose protection another
          person placed himself.
      (c) An advocate or pleader.
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                Let him who works the client wrong
                Beware the patron's ire.          --Macaulay.
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   3. One who encourages or helps a person, a cause, or a work;
      a furtherer; a promoter; as, a patron of art.
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   4. (Eccl. Law) One who has gift and disposition of a
      benefice. [Eng.]
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   5. A guardian saint. -- called also patron saint.
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   6. (Naut.) See Padrone, 2.
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   Patrons of Husbandry, the grangers. See Granger, 2.
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WordNet (r) 3.0 (2006):

patron saint
    n 1: a saint who is considered to be a defender of some group or
         nation