Green’s Dictionary of Slang

(US black/campus) underhand, unethical, untrustworthy, criminal.

1855		Life in Boston & N.Y. (Boston, MA) 14 Apr. n.p.: What kind of a place is the house next to the ‘brick house’ on Canal street? Rather shisty looking girls at the windows.
1993		Dr Dre ‘Deep Cover’ 🎵 Take a strap just in case one of his boys recognise my face. / Cause he’s a shisty motherfucker.
1993–2003		K. Beck on Urban Dict. 🌐 shiesty when a person is acting shadey...kinda I guess talking smack behind ur back... then acting like everythings peachy king when youre face to face with them. Man, youre shiesty!
1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Shiesty (adj.) 1. Slick, sly, or devious. [...] 2. Nasty, scummy.
2000		W. Shaw Westsiders 273: I’ll be the sheistiest motherfucker to my family, he says to himself.
2006		Times (Shreveport, LA) 2 Aug. 9/1: The industry is shady. Seedy. Sheisty.
2011		Hartford Courant (CT) 24 July PE04/4: It’not that we think they’re sheisty or are trying to pull a fast one one us.