mid·sum·mer (m?d?s?m??r)n.1. The middle of the summer.2. The summer solstice, on or about June 21 in the Northern Hemisphere.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.midsummer (?m?d?s?m?) n1. a. the middle or height of the summerb. (as modifier): a midsummer carnival. 2. (Astronomy) another name for summer solsticeCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014mid?sum?mer (?m?d?s?m ?r, -?s?m-) n. 1. the middle of summer. 2. the summer solstice, around June 21. adj. 3. of, pertaining to, or occurring in the middle of the summer. [before 900] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.