Green’s Dictionary of Slang

1. (US) unadulterated or very strong whisky.

1877		Dodge City Times 15 Sept. in Miller & Snell Why the West was Wild 278: They took unto themselves seven straights and a gin sling.
1882		Sydney Sl. Dict. (2 edn) 11: Straight - American bar talk for ‘neat’ liquor.
1907		‘O. Henry’ Trimmed Lamp (1916) 238: I managed to soak in a little straight or some spilled Martini [...] whenever I could.
1931		A. Hardin ‘Volstead Eng.’ in AS VII:2 87: Terms used for intoxicating liquor: Straight.
1950		Business Week 22 Apr. 24/2: Take a look at the table (above) and you will see that the straights and bonds are making their comeback [DA].
1969		L. Hadow Full Cycle 178: Evening, gents. Dash and two straights.

2. (S.Afr. black) a 750ml (26fl oz) bottle of spirits or beer.

1958		Casey ‘Kid’ Motsisi ‘Kid Hangover’ Casey and Co. (1978) 16: He can pay me back the three quid I loaned him so’s I can pay Aunt Peggy for the ‘straights’ I got on tick.
a.1968		D.C. Themba in Patel World of Can Themba (1985) 79: Boet Mike said, ‘Straight.’ And they brought a bottle of brandy that looked like guilty blood [DSAE].
1975		Drum (Johannesburg) 22 Apr. 13: Men like him, who never had the opportunity to own a straight of whisky, [...] never had three good meals in one day [DSAE].
1994		H. Masekela on TV1 16 Nov. n.p.: (People of South), A full bottle was a straight, then there was a three-quarter, and a half was a half-jack, and then there was a nip [DSAE].

3. (drugs) a tobacco cigarette.

1959		Esquire Nov. 70J: a straight: an ordinary cigarette.
1967		P. Thomas Down These Mean Streets (1970) 211: ‘Buying some cuchifritos?’ ‘Naw, just some straights.’ He walked over to the cigarette machine and got some smokes.
1971–2		C. Shafer ‘Catheads [...] and Cho-Cho Sticks’ in Abernethy Bounty of Texas (1990) 215: straight, n. – a cigarette.
1992		Bentley & Corbett Prison Sl. 65: Straight A seldom used term to indicate a manufactured cigarette. Straight is derived from the fact that the user remains ‘straight’ when smoking, and does not get ‘stoned.’.
1999		Observer 24 Oct. 29: We scored a deal and bummed a straight.

4. an unfiltered cigarette.

1965		H. Rhodes Chosen Few (1966) 62: I got straights in my lockerbox.
2000		C. Cook Robbers (2001) 4: Don’t buy those fuckin straights. Get some filters.