Entry 1 sense Webster, 1913 Substantiation /səb-stănˌ-chē-āsh'-ən/ · Sub·stan·ti·a·tion · IPA /səbstˌæntʃiːˈeɪʃən/ 01 n. The act of substantiating or proving; evidence; proof. 1. The act of substantiating or proving; evidence; proof.