a. [ Cf. F. agressif. ] 1. Tending or disposed to aggress; having or showing determination and energetic pursuit of one's own ends at the expense of others or mindless of others' needs or desires; characterized by aggression; making assaults; unjustly attacking; as, an aggressive policy, war, person, nation; an aggressive businessman; an aggressive basketball player; he was aggressive and imperious in his convictions; aggressive drivers. Opposite of unaggressive. [ 1913 Webster + WordNet 1.5 ]

No aggressive movement was made. Macaulay. [ 1913 Webster ]

2. Marked by self-confident ambition, vigorous competitiveness, energy and initiative; as, an aggressive young executive.
Syn. -- enterprising, pushful, pushing, pushy [ WordNet 1.5 ]

3. (Med., Biol.) Tending to grow or spread quickly; as, an aggressive tumor. [ Narrower terms: invasive (vs. noninvasive) ] AS
Syn. -- fast-growing(prenominal) [ WordNet 1.5 ]

4. Tending to initiate unprovoked attacks; initiating unprovoked military action; eager to fight; as, aggressive acts against another country.
Syn. -- belligerent. [ WordNet 1.5 ]

Narrower related terms: bellicose, combative, pugnacious, scrappy, truculent ; hard-hitting, high-pressure ; hostile (used of attempts to buy or take control of a business: "hostile takeover"; "hostile tender offer"); predatory, rapacious, raptorial, ravening, vulturine, vulturous . See also: assertive, hostile, offensive. [ WordNet 1.5 ]

-- Ag*gres"sive*ly, adv. -- Ag*gres"sive*ness, n. [ 1913 Webster ]