gangstester Share definition Flag Adj; 1. extremely cool; awesome. Often used with 'most,' 2. a gangster gone wrong 1. That's the most gangstester hat ever! 2. That gangstester is messed up, yo. gangstester by PeterPenguin December 31, 2008 0 0 Get merch Get the gangstester mug. Buy Now — $32.95 See more merch