Umbelliferone \Um`bel*lif"er*one\, n. (Chem.) A tasteless white crystalline substance, {C9H6O3}, found in the bark of a certain plant ({Daphne Mezereum}), and also obtained by the distillation of certain gums from the {Umbellifer[ae]}, as galbanum, asafetida, etc. It is analogous to coumarin. Called also {hydroxy-coumarin}.