Source : Webster's Revised Unabridged Dictionary (1913)

Missioner \Mis"sion*er\, n.
   A missionary; an envoy; one who conducts a mission. See
   {Mission}, n., 6. ``Like mighty missioner you come.''
   --Dryden.

Source : WordNet®

missioner
     n : someone sent on a mission--especially a religious or
         charitable mission to a foreign country [syn: {missionary}]