What is "acetoin"

n. (context organic compound English) The compound ''3-hydroxybutanone'' CH₃-CO-CH(OH)-CH₃ that is one of the constituents of the flavour of butter

Acetoin, also known as 3-hydroxybutanone or acetyl methyl carbinol, with the molecular formula is CHO, is a colorless or pale yellow to green yellow liquid with a pleasant, buttery odor. Acetoin is a chiral molecule. The form produced by bacteria is (R)-acetoin.