Entry 1 sense Webster, 1913 Peritoneal /pĕrˌ-ēt-ōn-ē'-əl/ · Per·i·to·ne·al · IPA /ˌpɛrətəˈni.əl/ 01 a. Of or pertaining to the peritoneum. 1. Of or pertaining to the peritoneum.(Anat.)