The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

   Missionary apostolic, a Roman Catholic missionary sent by
      commission from the pope.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Missionary \Mis"sion*a*ry\, a.
   Of or pertaining to missions; as, a missionary meeting; a
   missionary fund.
   [1913 Webster]

WordNet (r) 3.0 (2006):

missionary
    adj 1: relating to or connected to a religious mission [syn:
           missionary, missional]
    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: missionary,
       missioner]