A Mook is a foolish or ignorant person. The term was used widely in Mafia movies such as Mean Streets. The term originated in New York and has gained popularity in New Zealand, specifically Dunedin. The Australian MOOKS clothing company is named after it.
Mook can be pronounced with a long "oo" sound, as in "kook" or a short "o" sound as in look.
According to the PBS Frontline documentary, Merchants of Cool[1], "mook" refers to the target male audience of MTV for programs such as Jackass and other male-oriented "reality" series.