1. In certain royal families, especially that of imperial Austria, a nobleman having a rank equivalent to that of a sovereign prince.
2. Used as a title for such a nobleman.

[Obsolete French archeduc : arche-, arch- (from Old French; see arch-¹) + duc, duke (from Old French; see duke).]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.