Over-aged

Over-aged
A general breakdown of wine kept too long in cooperage or bottle; oxidized.
Oxidation
The changes in wine caused by exposure to air.

Lacklustre wine: over-aged, or not meant for ageing and kept too long, losing its freshness.
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Oxidized: Wine changed by contact with air, usually producing undesirable browning and sherry-like flavors. Over-aged.
pH: The measure of acid strength: the lower the pH, the higher the acid strength.

See also: Astringent, Acid, Bouquet, Champenoise, Canopy