Green’s Dictionary of Slang

1. (Aus.) to defeat, to overcome; to beat up.

1888		‘Rolf Boldrewood’ Robbery Under Arms (1922) 70: You ride straight, and don’t get up to any monkey tricks, or, by George, I’ll straighten you, so as you’ll know better next time.
1903		J. Furphy Such is Life 231: I’ll straighten you some of these times.
1944		C. Himes ‘He Seen it in the Stars’ in Coll. Stories (1990) 105: He wasn’t used to such hard work [...] and this slave was straightening him.
1955		E. Hunter ‘See Him Die’ in Jungle Kids (1967) 111: ‘They got him,’ said Aiello again. ‘You need straightening, you jerk,’ I said.

2. (UK Und., also straighten out) to bribe, usu. to bribe a police officer [i.e. to make straight adj.¹ (10)].

1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 11: Straighten (a case): To indice a prsecutor to drop case.
1937		J. Curtis There Ain’t No Justice 204: Every single one of your fights has bin fixed, see? Either the other bloke took the dive, or if that was a bit raw or if we thought we couldn’t straighten the other bloke, well we’ve straightened the ref.
1939		V. Davis Gentlemen of the Broad Arrows 213: You haven’t got the price to ‘straighten’ a screw.
1959		J. Gosling Ghost Squad 43: Usually they had the nightwatchman ‘straightened’ — which means bribed.
1961		J. Sparks Burglar to the Nobility 143: The Chief Magistrate [...] gave me a wink. I thought ‘Aye-aye, I’ve got the old geezer straightened’.
1972		P. Fordham Inside the Und. 23: The well-known euphemism of ‘straightening’ which means, of course, making crooked.
1989		T. Blacker Fixx 128: Local planning officers being straightened with briefcases packed with used fivers.
2000		J.J. Connolly Layer Cake 28: Jimmy’s one of the few guys in London who could straighten the very top old bill.
2011		J.J. Connolly Viva La Madness 25: An enterprising gent like Sonny would have people straightened out all over.

3. to sort a person out, to make them aware, to initiate them; thus straightening n.

1935		Z.N. Hurston Mules and Men (1995) 129: ‘He’s de King of de Beasts, but he ain’t no King of de World, now Sack,’ Dad Boykin spoke up. ‘He thought he was King till John give him a straightenin’.’.
1944		C. Himes ‘Let Me at the Enemy’ in Coll. Stories (1990) 38: I had to get them people straight an’ get ’em straightened fast.
1956		‘Hal Ellson’ ‘Cool Cat’ in Tell Them Nothing (1956) 84: He’s one guy I like [...] but that don’t mean I got to forget to straighten him.
1960		‘Lord Buckley’ Hiparama of the Classics 10: If they can’t get you straight, they know a Cat, that knows a Cat, that’ll Straighten you!
1972		D. Jenkins Semi-Tough 144: ‘Well, it makes you a man,’ I said. Shake said, ‘That’s right, boy. Give ‘em a few heart-breakers along the way. Straighten ‘em up’.

4. (also straighten up) to settle an account or debt.

1938		Pittsburgh Courier (PA) 16 July 11/1: Joe [has] alwatys been a prince of a fellow, goes to the cupboard [...] to ‘straighten’ the kids kicking up the boards [...] only to find it bare.
1946		Mezzrow & Wolfe Really the Blues 216: I’m short a deuce of blips but I’ll straighten you later.
a.1955		‘Good-Doing Wheeler’ in D. Wepman et al. Life (1976) 78: When I make that big sting, I’ll straighten you first thing.
1971		R.D. Pharr S.R.O. (1998) 217: ‘I figgered [...] I’d be able to straighten him out for the four [dollars]’.
1985		N. Pileggi Wiseguy (2001) 99: We’d usually straighten up in a garment-center restaurant called Bobby’s.
1995		J. Cameron Vinnie Got Blown Away 99: You got your honour to straighten Nicky.

5. to look after, to sort out a situation.

1960		‘Lord Buckley’ Hiparama of the Classics 8: They straightened the nanny goats.
1964		‘Return of Honky-Tonk Bud’ in D. Wepman et al. Life (1976) 69: I must confess I’ll straighten this mess.
1974		V.E. Smith Jones Men 24: You help me out, I’ll straighten you.

6. see straighten out v. (1)