ketol UK /ˈkiː.tɒl/US /ˈki.tɑl/ noun1 •A hydroxyketone (e.g., an acyloin).The 21-hydroxyl group in the α-ketol side chain is very easily esterified, and in many of the synthetic routes leading to these side chains the ketol acetate is still formed. — 1962 formsketols