The Collaborative International Dictionary of English v.0.48:
Dukedom \Duke"dom\, n. 1. The territory of a duke. [1913 Webster] 2. The title or dignity of a duke. --Shak. [1913 Webster]WordNet (r) 3.0 (2006):
dukedom n 1: the dignity or rank or position of a duke 2: the domain controlled by a duke or duchess [syn: duchy, dukedom]