Green’s Dictionary of Slang

1. (US) honestly.

1896		P.L. Dunbar ‘An Easy-Goin’ Feller’ in Lyrics of Lowly Life 110: I allus try / To do my dooty right straight up.
1898		Jack Thorp ‘Little Joe, the Wrangler’ in G. Logsdon Whorehouse Bells Were Ringing (1995) 35: He said if we would give him work he’d do the best he could, / Though he didn’t know straight up about a cow.
1963		A. Burgess Inside Mr Enderby in Complete Enderby (2002) 65: This here’s my fist [...] You’ll get it straight in the moosh, straight up you will.
1989		Eble Campus Sl. Mar.
1997		Simon & Burns Corner (1998) 65: If one crew’s product is too good to match straight up, a competing group might lace its package with a little strychnine.
2003		N. Green Angel of Montague Street (2004) 42: You go twelve and two [...] but both loses were DQs, you can’t even do that straight up.
2011		Elzhi ‘Represent’ 🎵 Straight up, shit is real, and any day could be your last.
2014		B. Kroeber ‘Be My Alibi’ in ThugLit Sept. [ebook] She straight up stole her landlord’s dog.
2022		J. Hannaham Didn’t Nobody Give a Shit 205: ‘Could I ask you something, straight up?’.

2. (also straight up and down) completely, unreservedly.

1988		W.D. Myers Fallen Angels 153: Kenny loved her straight up and down. He didn’t see any faults in her.
1996		UGK ‘Ridin’ Dirty’ 🎵 But these polices – they think they sharp as creases / or no reasons man, they straight up strippin cars to pieces.
2000		Observer 9 Jan. 18: So Bernard Manning asked me, straight up – I was the only black man in the place – where I was from.
2002		Simon & Burns ‘The Detail’ Wire ser. 1 ep. 2 [TV script] I didn’t think you were going to straight up hang me out on a line in a shitstorm.
2012		M. Wilkerson ‘A Clean White Sun’ in ThugLit Sept./Oct. [ebook] ‘Cats be strapped and straight up flyin’’.
2020		G. Armstrong Young Team 59: ‘See sir, straight-up famous!’.