war crimen. Any of various crimes, such as genocide or the mistreatment of prisoners of war, committed during a war and considered in violation of the conventions of warfare.war criminal n.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.war crime n (Law) a crime committed in wartime in violation of the accepted rules and customs of war, such as genocide, ill-treatment of prisoners of war, etc war criminal nCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014war? crime` n. Usually, war crimes. crimes committed against an enemy, prisoners of war, or subjects in wartime that violate international agreements or, as in the case of genocide, are offenses against humanity. [1940?45] war? crim`inal, n. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.