Source : Webster's Revised Unabridged Dictionary (1913)

Archduchess \Arch`duch"ess\, n. [Pref. arch- + duchess.]
   The consort of an archduke; also, a princess of the imperial
   family of Austria. See {Archduke}.

Source : WordNet®

archduchess
     n : a wife or widow of an archduke or a princess of the former
         ruling house of Austria