O·ka·nog·an also O·ka·na·gan (??k?-n?g??n) A river, about 185 km (115 mi) long, flowing southward from Lake Okanagan in southern British Columbia, Canada, to the Columbia River in north-central Washington.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.Okanagan (???k??n????n) n1. (Placename) a river in North America that flows south from Okanagan Lake in Canada into the Columbia River in NE Washington, US Length: about 483 km (300 miles). Also (US): Okanogan 2. (Peoples) Also: Okanogan or Okinagan a member of a North American Indian people living in the Okanagan River valley in British Columbia and Washington3. (Languages) Also: Okanogan or Okinagan the language of this people, belonging to the Salish familyCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014