- noun a colourless volatile liquid with an unpleasant smell.
- a colourless, volatile, natural chemical compound that exists in tiny quantities in good table wine and in large quantities in oxidised, spoiled wines. This chemical is in the group of compounds called aldehydes. It is produced when alcohol reacts with air during oxidation. Although in some cases this chemical can add complexity to a wine such as fino sherry, its pungent smell is normally noticed on spoiled wine.