a toxic, white crystalline substance, CHO, with the odor of vanilla, obtained from the tonka bean and certain plants or made synthetically: used in perfumes, soaps, etc.
See coumarin in American Heritage Dictionary 4
(ko͞oˈmər-ĭn)
noun
A fragrant crystalline compound, C9H6O2, extracted from several plants, such as tonka beans and sweet clover, or produced synthetically and widely used in perfumes.