1. Characterized by aggression: aggressive behavior.

2. Inclined to behave in an actively hostile fashion: an aggressive regime.

3. Assertive, bold, and energetic: an aggressive sales campaign.

4. Of or relating to an investment or approach to investing that seeks above-average returns by taking above-average risks.

5. Fast growing; tending to spread quickly and invade: an aggressive tumor.

6. Characterized by or inclined toward vigorous or intensive medical treatment: an aggressive approach to treating the infection.

7. Intense or harsh, as in color.