Green’s Dictionary of Slang

(US) unpleasant, crazy.

1993–2003		girl from sacto on Urban Dict. 🌐 sick ass gross or otherwise wrong They need to stop playing that sick ass Kid Rock music on the radio.
2004		N. Kelley ‘The Code’ in Brooklyn Noir 174: That ‘crazy motherfuckah with the sick-ass lyrics’.
2014		Baltimore Sun (MD) 29 Oct. T31/2: A sick-ass story about a creepy cult.