Green’s Dictionary of Slang

1. a drug user, usu. of some form of amphetamine.

1989		L.A. Times 8 Oct. 1: (Proquest) Methamphetamine [...] Users call themselves ‘tweakers.’.
1990		J. Wambaugh Golden Orange (1991) 50: He’s this little speed tweaker.
2005		Microgram Bulletin XXXVIII:2 35: 🌐 Chronic methamphetamine abusers – commonly known as tweakers – are the driving forces behind the most common methamphetamine myths.
2006		D. Winslow Winter of Frankie Machine (2007) : One look at his eyes tells Frank that the guy is a tweeker. Great, Frank thinks, a head full of crystal meth will make him a lot easier to deal with.
2009		J. Stahl Pain Killers 242: None of the tweakerettes so much as noticed when we entered.
2012		M. McBride Frank Sinatra in a Blender [ebook] He folded a crisp new piece of foil precisely. Like a veteran tweaker, his preparation ritual was an art form.

2. attrib. use of sense 1.

2005

C. Buzzell My War (2006) 22: These runaway tweaker hippie girls.

3. a crack cocaine user.

1988		S.F. Chronicle 19 Sept. A6: (Factiva) To Stan’s 16-year-old friend, John, the worst of the strung-out rock smokers – known as ‘tweakers’ – looks ‘like a bloodhound, man’ as they walk around with their backs stooped, searching the ground for fragments of rock discarded during police raids.
2007		C. Goffard Snitch Jacket 87: Keeping company with winos and tweakers at bottle clubs and all-night donut joints.
2013		J. Stahl Happy Mutant Baby Pills 117: A political tweaker named Spang had a teach-in on American foreign policy.
2020		D. Winslow ‘Broken’ in Broken 27: ‘This is what I hate about tweakers [...] You’re all so fucking stupid’.