look up any word, like pussy:
 
1.
verb. The act of beating someone with a weapon consisting of a canned food item inside of a sock. Believed to be derived from canned jack mackeral, the least expensive and abundantly available food in certain prison inmate stores.
(inmate 1) that dude keeps threatening me with a knife made out of a toothbrush.
(inmate 2) let's jack-mack him tonight after lights out.
by Bob Wible March 13, 2008