WordWeb Online

1. Having or showing determination and energetic pursuit of your ends
   "an aggressive businessman"; "an aggressive basketball player"; "he was aggressive and imperious; positive in his convictions"; "aggressive drivers"
    
2. Tending to spread quickly
   "an aggressive tumour";
   - fast-growing, strong-growing
    
3. Characteristic of an enemy or one eager to fight
   "aggressive acts against another country";
   - belligerent, chippy [N. Amer, informal]

See also: assertive, battleful, bellicose, combative, competitive, hard-hitting, high-pressure, hostile, invasive, in-your-face [informal], militant, obstreperous, offensive, predatory, pugnacious, rapacious, raptorial, ravening, rough, scrappy, self-asserting, self-assertive, truculent, vulturine, vulturous

Antonym: nonaggressive

Encyclopedia: Aggressive