n. [ F., fr. coumarou, a tree of Guiana. ] (Chem.) The concrete essence of the tonka bean, the fruit of Dipterix (formerly Coumarouna) odorata and consisting essentially of coumarin proper, which is a white crystalline substance, C9H6O2, of vanilla-like odor, regarded as an anhydride of coumaric acid, and used in flavoring. Coumarin in also made artificially. [ 1913 Webster ]