something that sucks horribly; stupid; fake; talentless

Wack - crap, shitty, no good.

A word used verbally by those who see themselves and their peers as gangster.
For someone to define something as wack, theyre saying its shit.

Hip hop artists (MCs, DJs, B-boys, etc) who are typically aspiring and full of themselves, yet their style is an insult to real hip hop because it (1) copies another artist's style, (2) is mainly driven by commercial aspirations, or (3) is basically incompetent with no hope of improving. Wack = weakly executed flashy moves in place of true substance.

Exp. To give something a negative stature.

When you commentating a ping-pong ball match

bad,not good. sometimes used in freestyle battlin'.

adj,'publicly decreed to be not very good by those of taste and distinction. That which makes an effort to achieve the approbation of the cultural vanguard but fails due to a lack of authenticity'

The word is of uncertain etymology. It first emerged from the highly non-standard forms of ebonics used by New York rappers in the late 1980s and early 1990s.