2. Adjective. (From hip-hop slang) bad (as in not good), inauthentic, of an inferior quality, contemptible, lacking integrity, inauthentic, lame, or strange. ¹
3. Adjective. (slang) crazy, mad, insane ¹
4. Noun. An eccentric; an oddball; a weirdo. ¹
¹ Source: wiktionary.com
Definition of Wack
1. a wacky person [n -S] / very bad [adj WACKER, WACKEST]