periodontitis (?p?r??d?n?ta?t?s) n (Dentistry) dentistry the inflammation of periodontal tissueCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014per?i?o?don?ti?tis (?p?r i o? d?n?ta? t?s) n. 1. inflammatory disease of the periodontium. 2. pyorrhea (def. 2). [1870?75] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.