Green’s Dictionary of Slang

1. (W.I./US black) to play or, of an instrument or of music in general, to be played so as to encourage vigorous dancing; thus jamming, dancing in an abandoned manner.

1933		W. Winchell On Broadway 11 Nov. [synd. col.] Add Slanguage [...] Ride is to ‘go to town’...Jam is to play it hotter than that.
1947		Cab Calloway ‘The Calloway Boogie’ 🎵 I woke up with the blues the other day, / The cats started jamming and they blew away. / With the Calloway Boogie.
1959		C. Himes Crazy Kill 9: Pigmeat was jamming on his tenor sax.
1971		H.E. Roberts Third Ear n.p.: jam […] v. 1. to play a musical instrument with fervor.
1980		E. Folb Runnin’ Down Some Lines 243: jam v. 1. Play a musical instrument with great vitality and feeling.
1993		K. Scott Monster (1994) 246: I [...] went into the den to jam some sounds.
1996		(con. 1964-65) B. Thorpe Sex and Thugs and Rock ’n’ Roll 110: The whole band was jamming, grinning from ear to ear.
2000		Guardian Guide 12–18 Feb. 25: ‘Jamming’ sounds too much like boogie.
2011		IOL News (Western Cape) 12 May 🌐 The guitar is part of the permanent collection at the Bob Marley Museum [...] ‘I wish I could still be jammin’ on it’.

2. (orig. US) of musicians, to play together without set scores or arrangement for the pleasure and the spontaneous music thus created.

1937		R.B. Nye ‘A Musician’s Word List’ in AS XII:1 46: jam, v. To improvise, play without written music.
1939		Goodman & Kolodin Kingdom of Swing 264: Real facility in improvising [...] can only be attained through as great deal of repetition and practice. By that I mean actually jamming and improvising with other musicians.
1946		Mezzrow & Wolfe Really the Blues 87: We hung out on the beach all day long, jamming our heads off.
1957		H. Simmons Corner Boy 27: Roy Milton’s Solid Senders jammed away.
1965		C. Brown Manchild in the Promised Land (1969) 243: They’d been around joints where the cats were jamming all the time.
1976		M. Braly False Starts 271: We jammed in Miss Smith’s Tea Room [...] his old lady on piano, oh, wow! jamming with her old man.
1988		D. Woodrell Muscle for the Wing 61: Did you just drop by to watch me jam on my back scratcher, Shade?
1999		E. Bunker Mr Blue 282: Legendary musicians came after their regular gigs to jam until the dawn.
2000		M. Manning Get Your Cock Out 19: The band started jamming freestyle, a kaleidoscopic space metal boogie from the stars.
2007		D.S. Mitchell Killer Tune (2008) 84: The music fast-jammed from midnight and slow-jammed from 3.30.

3. (US/UK black/campus/drugs, also jam down) to assoociate, to gather together; to have fun, a good time, also by taking drugs.

1945		Salt Lake Telegram (UT) 6 Apr. 5/2: [advert] Doin’ big time jamming? Don’t do a zombie...Be a sharp shark. Skin into these reet set of threads for slick chicks and swoon goons.
1953		L. Durst Jives of Dr. Hepcat (1989) 8: He shouted on the stroll where the riff masters whispered to the bug to get out of the rug because they were going to jam and jive for rugcutters holiday.
1977		(con. 1960s) D. Goines Black Gangster (1991) 270: Stay right here and keep on jamming.
1981		Eble Campus Sl. Fall 4: jam down – to have a good time.
1983		Toyes ‘Smoke Two Joints’ 🎵 Tokin’ on some sweet bud and jammin’ on a rootsy reggae-funky town.
1999		‘Master Pimp’ Pimp’s Rap 47: The club was jamming.
2001		Eble Campus Sl. Fall 6: JAM – hang out listening to and enjoying music.
2005		Jade LB Keisha the Sket (2021) 22: ‘U wanna jam and den ill escort u 2 ramelz yrd?’’.
2010		BBC News ‘Report on Teenage Slang’ 11 Mar. [radio] He wanted to jam with his bred’rins [...] He wanted to hang out with his friends.
2017		theculturetrip.com ‘Guide to London Slang 10 Jan. 🌐 Jam – relax, chill out (normally with drink and drugs).
2020		G. Krauze What They Was 15: You come out of your block [...] everyone is jamming [...] smoking and talking and whatever .

4. (US black) to talk forcefully, esp. in a group.

[1942		R. Mulvey ‘Pitchman’s Cant’ in AS XVII:1 Pt 2 Apr. 91/2: jamming. Selling to a whole crowd at once rather than to an individual].
1971		S. Stevens Way Uptown 144: A East Village fox was jamming to me about it.

5. (US black/campus, also jam back) to dance.

1972		D. Claerbaut Black Jargon in White America 70: jam back v. to dance.
1972		T.M. Kochman ‘The Kinetic Element in Black Idiom’ in Kochman Rappin’ and Stylin’ Out 165: In black English, ‘jam’ has been used to mean: (1) to play a musical instrument freely, (2) to dance, (3) to engage in sexual intercourse.
1981		Eble Campus Sl. Fall 4: jam – [...] to dance or to play music: The third floor was jamming at 3 this morning.
1995		L. Stavsky et al. A2Z 56/1: jam 4. v. to party.

6. (US campus) to do very well.

1982		Eble Campus Sl. Fall 3: jam – to do something well: I jammed on my homework last night [...] to do something better than another: Carolina will jam on Texas in El Paso.
1989		P. Munro Sl. U.
1997–2000		Da Bomb 🌐 16: Jamming: Move quickly; accomplish. I’m jamming on this paper.