slacker jack Share definition Flag a lazy, unemployable rapper. One who is rubbish at MC-ing. Shucks!! that Morris cannot even get a job in Mcdonalds, he is rubbish at MC-ing and can not rap. What a slacker jack! slacker jack by jonnyradfar December 6, 2006 0 0 Get merch Get the slacker jack mug. Buy Now — $32.95 See more merch