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.