noun acetoin a yellowish, pleasant-smelling liquid, C 4 H 8 O 2 , obtained from various carbohydrates, as glucose, by fermentation: used chiefly in the manufacture of flavors and essences. 1
noun acetoin (organic chemistry) The compound 3-hydroxybutanone CH3-CO-CH(OH)-CH3 that is one of the constituents of the flavour of butter. 0
