/ Dictionary / Index P periodontal disease: Meaning and Definition of Find definitions for: periodon'tal disease" Pronunciation: [key] any of various mixed bacterial infections that affect the soft tissues and bones supporting the teeth. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. periodontal periodontal membrane Related Content Daily Word Quiz: simian Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language