Green’s Dictionary of Slang

1. (orig. Aus.) abbr. aggressive.

1986		Canberra Times (ACT) 19 Jan. 27/2: Woodhouse admitted being ‘pretty aggro at the start.’ He had gone out a bit fast in the consolation final and didn’t come home too well.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 152: But the blowie turned out to be one of those aggro-type wax-nest hornets which took umbrage and cost him most of the sight in his right eye.
2016		T. Robinson Rough Trade [ebook] ‘I guess he got tired of waiting and decided to go all aggro about it’.
2020		D. Winslow ‘Sunset’ in Broken 206: ‘When Shafe drinks he can get aggro’.

2. hot-headed, wild, unpredictable.

1988		Canberra Times (ACT) 28 July 28/3: I had been pretty aggro up until I came out of the boys' home.
1991		J.T. Pickle Aus.-Amer. Dict. 4: AGGRO: Short for aggravated or aggressive.
1993		M.B. ‘Chopper’ Read How to Shoot Friends 106: He was always a touch on the aggro and paranoid side.
1997–2001		Online Sl. Dict. 🌐 aggro adj [...] 2. wild almost to the point of losing control, but effective. (‘When you got up on the table and started lecturing us, that was pretty aggro!’).
2003		K. Cage Gayle.
2005		P. Temple Broken Shore (2007) [ebook] He’s not aggro about me. It’s the world that’s the problem.
2011		C. Faust Choke Hold [ebook] [T]he short, aggro blond ducking behind the dumpster.
2019		C. Hammer Silver [ebook] ‘This aggro young shit knocked out that man’.
2020		G. Disher Consolation 49: I went there yesterday morning and was denied access [...] He was very aggro.