Rust Belt or rust beltn. A heavily industrialized area containing older factories, particularly those that are marginally profitable or that have been closed.rust?-belt? adj.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.rust belt n an area where heavy industry is in decline, esp in the Midwest of the US Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014rust? belt` n. (sometimes caps.) the Great Lakes states and adjacent areas of the eastern U.S. in which much of the work force has traditionally been employed in manufacturing and metals production. [1980?85] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.