Source : Webster's Revised Unabridged Dictionary (1913)

Dukedom \Duke"dom\, n.
   1. The territory of a duke.

   2. The title or dignity of a duke. --Shak.

Source : WordNet®

dukedom
     n 1: the dignity or rank or position of a duke
     2: the domain controlled by a duke or duchess [syn: {duchy}]