\San"to*nin\, n. [L. herba santonica, a kind of plant, fr. Santoni a people of Aquitania; cf. Gr. ?: cf. F. santonine.] (Chem.) A white crystalline substance having a bitter taste, extracted from the buds of levant wormseed and used as an anthelmintic. It occassions a peculiar temporary color blindness, causing objects to appear as if seen through a yellow glass.