Entry 1 sense Webster, 1913 Isentropic /īzˌ-ən-träp'-ək/ · I·sen·trop·ic · IPA /ˌaɪzəntrˈɑpək/ 01 a. Having equal entropy. 1. Having equal entropy.(Physics) Phrases & compounds Isentropic lines — lines which pass through points having equal entropy.