Entry 2 senses · 2 variants Webster, 1913 Incrassative · In·cras·sa·tive · IPA a. n. 01 a. Having the quality of thickening; tending to thicken. 1. Having the quality of thickening; tending to thicken. 02 n. A substance which has the power to thicken; formerly, a medicine supposed to thicken the humors. 1. A substance which has the power to thicken; formerly, a medicine supposed to thicken the humors.