Entry 1 sense Webster, 1913 Appendicitis /əp-ĕnˌ-dĭsˌ-īt'-ĭz/ · Ap·pend·i·ci·tis · IPA /əˈpɛnd.ɪ.saɪt.əs/ 01 n. Inflammation of the vermiform appendix. 1. Inflammation of the vermiform appendix.(Med.)