Green’s Dictionary of Slang

1. (drugs) cocaine.

1911		S.F. Call 27 Nov. 3/1: Among fiends, the drug [...] might be called just ‘C’ as morphine is called ‘M’ or ‘white stuff’.
1920		F. Williams Hop-Heads 17: The table was littered with [...] the ‘bindles’ (packages) of ‘c’ (cocaine).
1924		Truth (Brisbane) 22 June 12/5: ‘In my experience, nine out of 10 use cocaine or heroin, or ‘C’ and ‘H’ as the professional slang goes.
1930		J. Tully Shadows of Men 189: He knew that an addict ‘loaded on C’ was subject to wild and painful imaginings.
1945		W. Burroughs letter 24 July in Harris (1993) 3: Where do you secure the C? My own supply is utterly depleted.
1953		W. Brown Monkey On My Back (1954) 73: Of the two he vastly preferred cocaine but frequently used heroin because ‘C’ is hard to get.
1966		‘Do You Know What It Means?’ in D. Wepman et al. Life (1976) 158: Do you know what it means to have a supply of C and a supply of horse, / Not to need any connections because you’re the big boss.
1973		E. Droge Patrolman 167: Whether you call it snow, sugar, dust, coke, C, candy, girl, or Charlie, it’s still cocaine.
1981		D.E. Miller Bk of Jargon 337: C: Cocaine.
1998		(con. 1986) G. Pelecanos Sweet Forever 11: When he did high-grade C with Donna the two of them could go half the night.
2001		ONDCP Street Terms 5: C — Cocaine.
2010		Codella and Bennett Alphaville (2011) 12: ‘So, a little C or D sometimes?’ [...] ‘Yeah,’ he says, ‘I like coke, but [...] I’m not a dope addict’.

2. (US Und. ) constr. with the, the occupation of confidence trickery.

1960

L. Block ‘Badger Game’ in One Night Stands (2008) 29: ‘I’m working the C out of Philly’ [...] meant [...] that he was a confidence man who started originally in Philadelphia.

3. as the C, methcathinone.

2001

ONDCP Street Terms 21: The C — Amphetamine; methcathinone.