It’s slang for claiming. It’s a New York word. It can also be used in a way as like what you believe or think.
Him: I’m Jackin that he took my headphones
Her: You don’t know for sure so don’t Jack that
by Jayybabyyy February 11, 2020
Jackin it - The slang term for masturbate

-bat·ed, -bat·ing.
–verb (used without object)
1. to engage in masturbation.
–verb (used with object)
2. to practice masturbation upon.
Origin: 1855–60; < L masturb&#257;tus, ptp. of masturb&#257;r&#299; to engage in masturbation

—Related forms
mas·tur·ba·tor, noun Unabridged (v 1.1)
You: Where is Nick?
Me: Oh, he is at his house jackin it to some porn.
by SpERRM November 5, 2007
jackin is another word for stealing.
Example can be found on Ice Cube's Jackin for beats.
by trock March 8, 2005
Too pleasure one's self in a sexual way
T: dude i was jackin it major last night!
by Martyn Mcfly November 22, 2007
-Whats up tho.Where u comin from?
-Shit,gotdamnit.Jst got thru jackin.
-Eh gotta get it how ya live.

Girl:Ugh.Cant stand that btch.Always talkin that shit.
Instigator:Hell,gone get the jackin wit her then.

*If u evr seen Next Friday...When Craig was in the bthrm. Pops was like "Craig.Off yo ass and on yo feet.Aint no time to "beat yo meat"."Yeah.Thats called jackin.
by U herr me May 4, 2008
i'm jackin that nigga fo' his ice
by Mark April 15, 2003