ag·gres·sive [? gréssiv] adjective 1. likely to attack: showing a readiness or having a tendency to attack or do harm to others 2. attacking: attacking or taking action without provocation or without waiting for an enemy to make the first move 3. ?assertive: characterized by or exhibiting determination, energy, and initiative an aggressive investment policy 4. medicine spreading quickly: describes a disease or a pathological growth such as a tumor that spreads or grows quickly 5. extreme sports emphasizing stunts: describes a type of in-line skating, skateboarding, or snowboarding that focuses on performing stunts -ag·gres·sive·ly, adverb -ag·gres·sive·ness, noun Note that the correct spelling of aggressive and aggression is with -gg- and -ss-.