sto·ma·ti·tis (st??m?-t??t?s)n. Inflammation of the mucous tissue of the mouth.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.stomatitis (?st??m??ta?t?s; ?st?m-) n (Pathology) inflammation of the mouth stomatitic adjCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014sto?ma?ti?tis (?sto? m??ta? t?s, ?st?m ?-) n. inflammation of the mouth. [1855?60] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.