Green’s Dictionary of Slang

(US black) the supposedly sophisticated style of driving a car, with one’s elbow out of the window and the body leaning in the same direction; thus, fig., an attitude to life and a lifestyle; in cit. 1998 the word gangster is implicit.

1974		William DeVaughn ‘Be Thankful (For What You’ve Got)’ 🎵 Diamond in the back, sunroof top / Digging the scene with a gangster lean.
1986		The Real Roxanne ‘Bang Zoom’ 🎵 You, the one with the gangster lean.
1993		Dr Dre ‘Nuthin But a G Thang’ 🎵 Fallin’ back on that ass with a hellified gangsta’ lean.
1998		(con. 1986) G. Pelecanos Sweet Forever 80: Monroe sat real low in the driver’s seat, his forearm resting on the lip of the open window, his wrist dangling. Had to have the arm outside the window for the full lean.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 76/1: gangster lean n. the lifestyle, attitude and personality traits of a gang-member.
2002		‘Touré’ Portable Promised Land (ms.) 156: We Words (My Favorite Things) [...] Gangsta lean. Pushin up daisies. Deaded.
2004		I. Perry Prophets of the Hood 99: The first two lines tie African spiritual practices to the politics of the body: the gangster lean, black coolness seen in daily life in Brooklyn.
2012		Rock Mecca ‘Gangsta Boogie’ 🎵 Could you deal with this gangsta lean straight from Queens.