Definitions of aggressive:

• adjective:   characteristic of an enemy or one eager to fight

  Example: "Aggressive acts against another country"

• adjective:   tending to spread quickly

  Example: "An aggressive tumor"

• adjective:   having or showing determination and energetic pursuit of your ends

  Example: "An aggressive businessman"

• adjective:   marked by aggressive ambition and energy and initiative

  Example: "An aggressive young exective"