A religious cult, centered on the worship (and/or drinking) of Jack Daniels, both the drink as well as the man. (assumed deceased.)
Man 1: Dude, thats your 3rd bottle of jack today!
Man 2: What do you expect from a believer in Jackism?
Someone who is skilled in the drinking of large quanitities of Jack Daniels, usually in an Alcoholic mannor.
Man 1: Dude, you need to cut down on drinking jack...
Man 2: i would, but I'm a Jackaholic. It's a life choice, really.