Entry 1 sense Webster, 1913 Diastase /dī'-əs-tāsˌ/ · Di·a·stase · IPA /ˈdaɪəsteɪz/ 01 n. A soluble enzyme, capable of converting starch and dextrin into sugar. 1. A soluble enzyme, capable of converting starch and dextrin into sugar.(Physiol. Chem.)