This means when a whole bunch of musicians get together play some chords for about a minute saying random lyrics and then go on playing for 19 more minutes.
Phish has super long jam sessions.

Dude Bill and I had a 35 minute jam session last night.
by Chris February 7, 2005
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a gangbang of sexual intercourse with 4 or more guys on one girl.
That bitch is sick she had a jam session with 6 guys
by Anonymous July 14, 2003
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When a group of bros take turns having sex with a jar or squeeze bottle of jam or jelly (preferably squeeze bottle). Can substitute marmalade as well. No preserves for fear of chunks in urethra.
I got together with my old college roomates this weekend and we had a solid 2 hour jam session.
by The Real Wiz 76 July 16, 2016
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When u listen to music and dance to it with more then 1 person
by krista January 4, 2004
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Bringing the wood to a female sexual partner. The opposite of making sweet love. An almost violent sexual encounter.
Where did you wander off to after hours last night.? Oh, man I slide over to Jenny's house for a Jam /Beat session.
by phrasee January 6, 2010
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When you jack-off you're just rockin' a fuggin' jam sesh bro!!!
Kid: Hey man, what are you gonna do later?
Bro: I'm just gonna creep on some bitch's facebook pics and rockin' a jam session.
Kid: Tight. Samesies.
by jam time November 28, 2009
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When you make music with your homies while jerking off
Person A: I feel like making some rad music but also like beating tf out of my meet

Person B: then let's get the boys together and do a Jizz-Jam-Session
by smol Karl, Coori May 29, 2018
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