tr.v. un·round·ed, un·round·ing, un·rounds
To pronounce (a sound) with the lips in a flattened or neutral position.
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.
(Linguistics) to release (lips) from a rounded position, esp in pronunciation
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
1. to articulate (an ordinarily rounded vowel) without rounding the lips.
2. to extend (the lips) laterally in a spread or neutral position.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.