Gook is a Korean word used as a bad slang towards people of Asian culture. It's original meaning translates to "people of". Americans are known as Mi-gook, Korean's are Han-gook, and so on. The word Gook was probably taught to American GI's during the Korean War, who bastardized it's use. It surfaced again and was used by GI's who later fought in VietNam. It's still used as a common, non-derogatory, word in Korea and as a slang in other parts of the world.
Definitions include: after using meth standing in front of a mirror and digging on ones face. falsely thinking ones face has a blemish or pimple and due to the drugs the person continue to dig out a blemish that does NOT exist.