Second World Warn. World War II.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.Second World War n (Historical Terms) another name for World War II Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014World War II n. the war between the Axis and the Allies, beginning on Sept. 1, 1939, with the German invasion of Poland, and ending with the surrender of Germany on May 8, 1945, and of Japan on Aug. 14, 1945. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.