Green’s Dictionary of Slang

1. (US Und.) to lie, to work a confidence trick, to fool a victim; usu. as jeffing.

1960		C. Cooper Jr Scene (1996) 36: Naturally, the saleslady said, doing what Marsha Lee called ‘jeffing’.
1985		T.R. Houser Central Sl. 31: jeff [...] To lie to. To rumor. To bullshit. ‘I ain’t jeffin’, man, I put your ride behind the house.’.
1992		Bentley & Corbett Prison Sl. 46: jeffin’ An old expression meaning to tease someone by telling him many things that are either untrue or exaggerated. Jeffin’ has expanded to encompass all forms of lying, but it is generally used in a lighter, more humorous vein.

2. (US prison) to tease, to joke with.

1969		‘Iceberg Slim’ Pimp 59: The junkie bastard was jeffing on me, lashing me with contempt and scorn.
1981		Maledicta V:1+2 (Summer + Winter) 268: A prisoner joking with another is jeffin with the person.
2000		Other Side of the Wall: Prisoner’s Dict. July 🌐 Jeff: Joke, play.

3. (US black) to talk, to chatter, esp. to seduce, to fool or deceive with a ‘line’; thus tight jeff, well-rehearsed patter; slack jeff, spontaneous ad-libbed chatter.

1983		R. Klein Jailhouse Jargon and Street Sl. [unpub. ms.].
2002		(con. 1998–2000) J. Lerner You Got Nothing Coming 137: On-the-leg piece a shit! [...] Warden-jeffing suck-ass! [...] Punk-ass stanky-on-the-hang-low bitch motherfucker!

4. (US black) to behave obsequiously, esp. towards whites, to humiliate oneself.

1960		C. Cooper Jr Scene (1996) 38: Alice looked guilty, then said, false-smiling, jeffing, ‘He sold it to me.’.
1970		G. Cain Blueschild Baby 36: ‘You oughta know [whites] ain’t never told the truth about nothing, especially about you [...] Only brothers they going to tell you about is those good jeffin niggers’.
1997–2000		College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Jeff (verb) To kiss the ass of someone you know doesn’t like yo ass.