Source : Webster's Revised Unabridged Dictionary (1913)

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

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

Source : WordNet®

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