Green’s Dictionary of Slang

mack adj.

also mac
[mack n.2 (1)]
(US black)

1. masculine in appearance and behaviour.

[[WI]J.B. Moreton West India Customs and Manners 157: Tajo, tao, tajo! my mackey massa! [...] I’ll please my mackey massa! I’ll jig to mackey massa! / I’ll sweet my mackey massa!].
[UK]J. Colebrook Cross of Lassitude 264: I want a man to be mac and aggressive, and not just a yard dog.

2. anything pertaining to a pimp, such as attitude, philosophy, automobile or clothes.

[US]‘Soulful Spider’ ‘Pimp in a Clothing Store’ in Milner & Milner (1972) 286: Young man walked in, Jack, in black on black with a gray tie. Mack hat hanging down, pimp shades sockin’ it to you from the cue view.
[US]Nasir Jones ‘Live Now’ 🎵 Since we met a while back, and your style was mack.

In phrases

get mack (v.)

(US black) to become enthusiastic, excited.

Ted Yates New York Town 1 Nov. [synd. col.] Harlem (getting mack to the land of the free and the home of the brave) is all worked up.