Coumarin \Cou"ma*rin\ (k[=oo]"m[.a]*r[i^]n), 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.

Source: Webster's Revised Unabridged Dictionary (1913)