Aq·ui·taine (?k?w?-t?n?) A historical region of southwest France between the Pyrenees and the Garonne River. The duchy of Aquitaine was joined with France after the marriage of Eleanor of Aquitaine to King Louis VII in 1137, but its possession was disputed after her subsequent marriage to Henry II of England.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.Aquitaine (?ækw??te?n; French akit?n) n (Placename) a region of SW France, on the Bay of Biscay: a former Roman province and medieval duchy. It is generally flat in the west, rising to the slopes of the Massif Central in the northeast and the Pyrenees in the south; mainly agricultural. Ancient name: Aquitania Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Aq?ui?taine (?æk w??te?n) n. 1. Latin, Aq`ui?ta?ni?a. a historic region in SW France, formerly an ancient Roman province and medieval duchy. 2. a metropolitan region in SW France. 2,796,000; 15,949 sq. mi. (41,308 sq. km). Cap.: Bordeaux. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.