Hai·nan (h??nän?) An island of southern China in the South China Sea, separated from Leizhou Peninsula by a narrow strait. It constitutes China’s smallest province.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.Hainan (?ha??næn) or Hainan Taon (Placename) an island and province in the South China Sea, separated from the mainland of S China by the Hainan Strait: part of Guangdong province until 1988; mainland China’s largest offshore island. Pop: 8 110 000 (2003 est). Area: 33 572 sq km (12 962 sq miles)Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Hai?nan (?ha??n?n) n. an island in the South China Sea, separated from the mainland by Qiongzhou Strait: constitutes a province in S China. 7,110,000; 12,430 sq. mi. (32,200 sq. km). Cap.: Haikou. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.