Definition - What does Aggressive mean?
"Aggressive" is the adjective used to describe a wine that is harsh in character. This can be noticed on the taste, its texture or both. "Aggressive" is often used to say that a wine is out of balance with high tannin or high acidity levels. These wines can sometimes be corrected with aging.
WineFrog explains Aggressive
When a wine gives one the sensation of being over-drying on the palate or having too much tannin, it can be described as "aggressive". In other aspects, an aggressive wine can also be excessively harsh or tart in its acidity.
Sometimes these characteristics indicate that the wine is a young wine. These are wines that often have the ability to correct themselves with proper aging in a cellar. Harsh tannins can soften over time and "fall" out of the wine. Likewise, acidity can also soften with aging, thus making the wine softer and more balanced.