O·a·hu or O’a·hu (?-ä?ho?o) An island of central Hawaii between Molokai and Kauai. It is the chief island of the state, with major tourist areas, including Waikiki Beach and Diamond Head, and a US naval base at Pearl Harbor.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.Oahu (?????hu?) n (Placename) an island in central Hawaii: the third largest of the Hawaiian Islands. Chief town: Honolulu. Pop: 876 151 (2000). Area: 1574 sq km (608 sq miles)Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014O?a?hu (o??? hu) n. an island in central Hawaii: third largest island of the state. Chief city: Honolulu. 630,528; 589 sq. mi. (1525 sq. km). Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.