Entry 1 sense Webster, 1913 Diagnose /dīˌ-əg-nōs'/ · Di·ag·nose · IPA /ˈdaɪ.əɡˌnoʊs/ 01 v. t. & i. To ascertain by diagnosis; to diagnosticate. See Diagnosticate. 1. To ascertain by diagnosis; to diagnosticate. See Diagnosticate. See: Diagnosticate