New Year’s Dayn. January 1, the first day of the year, celebrated as a holiday in many countries.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.New Year’s Day n Jan 1, celebrated as a holiday in many countries. Often (US and Canadian informal) shortened to: New Year’s Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014New? Year’s` Day? n. January 1, celebrated as a holiday in many countries. [1150?1200] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.