Entry 1 sense Webster, 1913 Deterioration /dĭt-ĭr'-ē-ẽr-āshˌ-ən/ · De·te·ri·o·ra·tion · IPA /dəˌti.ɹi.əˈɹeɪ.ʃən/ 01 n. The process of growing worse, or the state of having grown worse. 1. The process of growing worse, or the state of having grown worse.