Green’s Dictionary of Slang

1. a million, usu. of money.

1967		P. Thomas Down These Mean Streets (1970) 72: Thanks a mil, sir.
1972		G.V. Higgins Friends of Eddie Coyle 170: They made what, about a quarter of a mil in a month?
1982		A. Maupin Further Tales of the City (1984) 40: Two mil a movie must soften the blow.
1990		J. Wambaugh Golden Orange (1991) 219: The house across from Margie’s is in escrow for nearly seven mil!
2007		W. Ellis Crooked Little Vein 16: You’re just sending me into the wilds with half a mil and this?
2014		Wiley ‘From the Outside’ 🎵 Five bills for a grime beat, that's real / [...] / I’mma stack till I get mils.
2017		D. Winslow The Force [ebook] Condos in the new high-rises buildings go for two and a half a mil.
2020		D. Winslow ‘Crime 101’ in Broken 106: Maybe it’s the eleven mil, the walkaway score.

2. a milligram, usu. of a drug.

1997		L. Davies Candy 121: We talked about a quick methadone reduction program: start on just 40 mils, go to zero in two months, something like that.
2002		(con. 1981) W. Self Dorian 37: ‘What’s he on nowadays?’ [...] ‘Same as ever, five-mil Dexies in the day, tombstones or bombers if he’s out on the razzle.’.