Definition - What does Hard mean?
Hard is a term used to describe young, red wines which would benefit from more aging. The characteristics of a hard wine is one with high acidity and high tannin content. This is not necessarily a sign of bad quality, but of a wine that needs aging before it can be properly enjoyed.
WineFrog explains Hard
When a wine is described as hard it is usually because of the mouthfeel it presents on the palate. Hard wines can be harsh on the palate, as those with high acidity or tannin can attack the mouth in an unpleasant manner.
High acidity can make one's mouth pucker, making other characteristics of the wine unnoticeable and unenjoyable. Harsh tannin or high tannin content can leave your mouth excessively dry. However, both of these qualities can be softened with proper bottle-aging.