Green’s Dictionary of Slang

new jack adj.

[new jack n.]
(US black)

1. superficial, flashy, meretricious.

[US]EPMD ‘You Gots To Chill’ [lyrics] To the average MC I’m known as The Terminator. / Funky beat maker, new jack exterminator.
[US]N. Kelley ‘The Code’ in Brooklyn Noir 187: He had the aura of a champion boxer, a new jack Muhammad Ali.
[US]Codella and Bennett Alphaville (2011) 293: This new jack nigga all muscled up and shit just outta jail a few months.

2. in tune with the contemporary young black culture.

Cooper & Wright New Jack City [film script] I need cops that know these streets. I need new jack cops to take down a new jack gangster.
[US]N. George ‘Cool vs. Chilly’ in Buppies, B-Boys, Baps and Bohos (1994) 72: The new jack swing of Teddy Riley and Tammy Lucas on ‘Is It Good to You.’.
[US]Source Aug. 154: Whether you’re an old-school biker or a new-jack rider, we’ve got bikes that’ll get the most burn this summer.

3. naive, unaccomplished.

[US]Codella and Bennett Alphaville (2011) 221: I don’t want some new jack white kid rookie shooting me in the back.
[US]G. Hayward Corruption Officer [ebk] cap. 10: The day went on with me doing more new jack shit.

In compounds

New Jack City (n.)

(US black) Detroit, New York City or any other city with a thriving ghetto lifestyle.

[US]M. van Peebles [film title] New Jack City.
[US]R.C. Cruz Straight Outta Compton 62: [note] Although this is a fictional story, there is a New Jack City in every major metropolis in this country.
[US]‘Touré’ Portable Promised Land (ms.) 155: We Words (My Favorite Things) [...] New Jack City. Chocolate City. Soul City.