Green’s Dictionary of Slang

1. of drink, adulterated, diluted, weakened.

1927		Stephen Graham N.Y. Nights 75: Our rye is cut many times over.
1932		V.F. Nelson Prison Days and Nights 205: Plenty of liquor – good stuff, too; none of this cut stuff.
1961		‘Lou Rand’ Gay Detective (2003) 77: ‘Say, Joe, this is sure better liquor than we got out there.’ Cannelli laughed. ‘It better be. It isn’t cut.’.
1966		(con. 1958) R. Farina Been Down So Long (1972) 48: Nasty lush: ethyl alcohol cut with Gallo sauterne and tequila.

2. (drugs) adulterated, diluted.

1949		N. Algren Man with the Golden Arm 24: Nifty Louie was pushing a heavily cut grade of morphine.
1952		E. Reid Mafia 68: In Italy [...] the price per kilo ranged from $1000 to $ 1500; you can figure the dope pushers’ profit on the cut stuff they sold their customers.
1966		T. Keyes All Night Stand 121: I’ve got this very good congo, not cut, ya know.
1975		B. Greer Slammer (1977) 90: I could get an ounce off the street — uncut — five grand.
1989		M. Amis London Fields 36: The heroin, the cut coke, the Temazepan, the dihydrocodeine he has always refused.
1993		I. Welsh Trainspotting 12: That meant thit it [i.e. heroin] wisnae cut too much, wi anything too toxic.
2007		C. Goffard Snitch Jacket 40: A few ounces of pot, 10 or 12 skankweed dime bags generously cut with oregano.
2010		Codella and Bennett Alphaville (2011) 119: A pair of upper tier main dealers [...] are stepping on already cut dope he fronts to them.
2013		D. Whish-Wilson Zero at the Bone [ebook] It was uncut. He never used cut. She’d have been used to street shit, 10 per cent pure. But this was all pure. She’d hit ten times her usual spike.