Webster’s Revised Unabridged Dictionary · 1913 Propenyl Pro′pe·nyl (prō′pē·nĭl), n. [Propene + -yl.] (Chem.) A hypothetical hydrocarbon radical, C3H5, isomeric with allyl and glyceryl, and regarded as the essential residue of glycerin. Cf. Allyl, and Glyceryl. ‹ Propensity Propepsin ›