n. [ Salicylic + aldehide. ] (Chem.) A thin, fragrant, colorless oil, HO.C6H4.CHO, found in the flowers of meadow sweet (Spiraea), and also obtained by oxidation of salicin, saligenin, etc. It reddens on exposure. Called also salicylol, salicylic aldehyde, and formerly salicylous acid or spiroylous acid. [ 1913 Webster ]