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 Umbelliferae, as galbanum, asafetida, etc. It is analogous to coumarin. Called also hydroxy-coumarin. Its strong fluorescence under ultraviolet light makes it useful in analytical biochemistry, as, for example, to detect phosphatase activity by hydrolysis of umbelliferyl phosphate. [ 1913 Webster +PJC ]