angry, and behaving in a threatening way; ready to attack

determined and acting with force in order to succeed

a very aggressive advertising campaign

We need to get more aggressive in our approach.

The firm is extremely aggressive in seeking new markets.

developing quickly and difficult to treat 

Doctors diagnosed her with a rare and aggressive cancer, which was feared to be incurable.

using all possible treatment options in order to extend somebody’s life 

Nicholas was diagnosed with the rare disease in November and has undergone aggressive treatments since then.

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