Definition - What does Flabby mean?
Flabby is a negative term that is used to describe a wine with a low acidity and a high pH, which means that it is unbalanced and will not have a quality or enjoyable taste. Flabby wines are heavy-tasting and lacking in structure, making them inactive on the palate's tastebuds. Due to the lack of acid, these wines are syrupy or sweet with a limp, sickening taste with the tannins consuming the natural fruity flavors of the wine.
WineFrog explains Flabby
A flabby wine does not have the regular structure to be expected of quality wines. This is caused when overripe grapes are selected and used past the time of their prime ripening. Some characteristics of flabby wines include high alcohol content, high tannins, low in fruity aspects and a deep, brown coloring.
A flabby wine can be caused by deficiencies in tannin/acid balance and bottling the wine with too much oxygen in it. Winemakers can avoid these effects by adding tartaric acid during the fermentation process and slowly exposing the air to the bottle over longer periods of time.