Green’s Dictionary of Slang

1. (drugs) cocaine.

1959		J.E. Schmidt Narcotics Lingo and Lore.
1972		C. Bukowski Erections, Ejaculations etc. 142: And there was the Big C. Big H. And Hash. Mary. Name it.
1981		D.E. Miller Bk of Jargon 336: big C: Cocaine.
2001		ONDCP Street Terms 3: Big C — Cocaine.
2008		Post-Star (Glen Falls, NY) 3 Aug. 18/5: There are many slang terms for cocaine [...] big C, blanco, blast, [...] girl, heaven, Mama Coca, [...] pimp, she [...] toot, trains, stardust.

2. (also C) cancer.

1967		W. Murray Sweet Ride 99: ‘He’s had a lung removed.’ ‘The big C?’ ‘Yes.’.
1975		L. Block Topless Tulip Caper in Affairs of Chip Harrison (2001) 600: Some knife-happy surgeon decided I had the big C.
1978		New Scientist 19 Oct. 156: Critics of the US government’s efforts to combat cancer have castigated its failure to spend more money on investigating possible links between diet and the ‘big C’.
1986		T. Philbin Under Cover 21: He was preoccupied with his own mortality and expected to be struck down any time by ‘The Big C’.
1999		Guardian G2 16 Aug. 5: John Wayne, before the ‘Big C’ took one of his lungs, boasted that he used to smoke 100 cigarettes a day.
2009		J. Joso Soothing Music for Stray Cats 10: She’d passed away. The big ‘C’ as people call it.
2012		(con. 1980s) I. Welsh Skagboys 85: —She’s goat the big C. —Cancer? ah goes.
2021		T. Pluck Boy from County Hell 233: ‘Andre’s got the big C’.

3. cirrohosis of the liver.

2000

N. Griffiths Grits 151: The big C it was that took er, gets us all in-a end like, that Cirrhosis.