riff, v. — Green’s Dictionary of Slang

riff v.

1. (orig. US black) to chatter, to talk.

1944		D. Burley N.Y. Amsterdam News 13 May 6B: He riffed that he’d been tabbed for the ‘B’ brigade.
1959		A. Anderson ‘Dance of the Infidels’ in Lover Man 155: We’d get juiced and have ourselves an A-grade ball, listening and riffing.
1969		N. Spinrad Bug Jack Barron 19: Riff with Luke.
1978		R. Price Ladies’ Man (1985) 47: Now I was riffing with equal intensity about good grooming.
2007		C. Goffard Snitch Jacket 70: They riffed that way for a few minutes.
2017		T. Spicer Good Girl Stripped Bare 241: Alan and I riff about radio and politics.

2. (US campus) to boast or exaggerate; also as n.

1974

Eble Campus Sl. Apr. 2: rif n. – an exaggerated tale; v., to exaggerate.

3. (US) to complain.

1995		(con. 1985–90) P. Bourjois In Search of Respect 26: Ray’s been riffin’ [complaining]? He’s gonna come in and say I’m not allowed no more to associate?
2011		G. Hayward Corruption Officer [ebk] cap. 41: She’s riffing about me not passing my classes.

4. (US campus, also riff on) to take advantage of someone.

1981

Eble Campus Sl. Mar. 6: riff – person who takes advantage of another; riff on – to take advantage of another: Hey, don’t riff on me, man.

5. to inform on; to reveal facts about.

2001		(con. 1964–8) J. Ellroy Cold Six Thousand 253: Jane riffed on De Kalb. Miss Gersh. Miss Lane. The boy with lupus.
2011		Guardian 26 Mar. 3/2: He even riffs on the health service secretary’s expenses record.
2016		V. McDermid Out of Bounds (2017) 356: She was [...] riffing on conceptual art when she ought to be [etc].

6. to offend.

1991		De La Soul ‘Millie Pulled a Pistol on Santa’ 🎵 Anyone who’d riff on me, I’d pop their dome like bubbles’.
1994		C. Major Juba to Jive.

7. to take as one’s conversational or behavioral point of departure.

1994		T. Wolff In Pharoah’s Army 205: I couldn’t tell [...] if he actually thought he resembled a person with a mustache or was just riffing on the idea.
2007		W.J. Cobb To the Break of Dawn 109: Ralph Ellison [...] placed the unnamed protagonist of Invisible Man in an unnamed municipality, painted him black, and then riffed on the nature of epidermal camouflage.