Source : Webster's Revised Unabridged Dictionary (1913)

Missionary \Mis"sion*ary\, n.; pl. {Missionaries}. [Cf. F.
   missionnaire. See {Mission}, n.]
   One who is sent on a mission; especially, one sent to
   propagate religion. --Swift.

   {Missionary apostolic}, a Roman Catholic missionary sent by
      commission from the pope.

Missionary \Mis"sion*a*ry\, a.
   Of or pertaining to missions; as, a missionary meeting; a
   missionary fund.

Source : WordNet®

missionary
     n 1: someone who attempts to convert others to a particular
          doctrine or program
     2: someone sent on a mission--especially a religious or
        charitable mission to a foreign country [syn: {missioner}]