Source : Webster's Revised Unabridged Dictionary (1913)

Expeditionary \Ex`pe*di"tion*a*ry\, a.
   Of or pertaining to an expedition; as, an expeditionary
   force.

Source : WordNet®

expeditionary
     adj : (used of military forces) designed for military operations
           abroad; "the French expeditionary force in Indochina"