wack
Meaning
Very bad, poor, or disappointing in quality
Unconventional or odd, often in an amusing or interesting way
Usage
The movie's special effects were so wack that we left the theater early.
He's into some really wack fashion, but it suits his personality.
That new policy is completely wack and unfair to students.
Etymology
The adjective 'wack' emerged in American slang during the late 20th century. It is widely considered a back-formation from the older term 'wacky', meaning 'eccentric or irrational', which itself may derive from the earlier 'whacky' or from 'whack' meaning 'a blow'. The semantic evolution likely moved from the sense of being 'struck' or 'out of order' to meaning 'foolish' and finally to its dominant modern sense of 'terrible' or 'uncool'. Its adoption and popularization are heavily tied to hip-hop culture and vernacular.
Analysis
The word 'wack' is a simplex form. It is a slang term of uncertain origin, likely a back-formation or alteration of the earlier term 'wacky'.