When you take a long piece of feces that you have made and freeze it, later shoving it up your partner's nose, then shoving it in your partner's vagina causing it to melt into diarrhea which is then soaked up with rice and put into the blender and made into a smoothie, then the partners throw the smoothie up in each others' anuses.
Me and my girl do the Mississippi cold pocket errday.
Similar to an Alabama hot pocket in which a man deficates in a womans vagina and has sex with said vagina afterwards. The difference is the Mississippi cold pocket is performed on a dead and cold body, preferably a hooker.
Ross just did a Mississippi cold pocket on the dead hooker in the trunk!