Entry 1 sense Webster, 1913 periodontitis /(pĕr`ē*ō̇*dŏn*tī"tĭs)/ · per·i·o·don·ti·tis · IPA 01 n. A disease that attacks the gum and bone around the teeth. 1. A disease that attacks the gum and bone around the teeth.(Med.) Syn. periodontal disease.