Compulsive spending is ones "need" to shop. Spending more money than one has, or uses money that one has reserved for other things, such as paying bills, mortgage/rent, etc., and they spend it on items that they don't need but feel as though they do need the item(s) and cannot live without buying that particular item(s) right then and there.
Some may laugh it off, even make fun of this type of behavior. For example, the movie, Confessions of a Shopaholic. Like anything else, shopaholics can go to treatment/programs and even get the support they need to make a budget and stick to it, essentially breaking the cycle one step at a time, as one may do if they were a cigarette smoker, on drugs, or even an alcoholic. Granted every program and every person is unique and different, and those seeking help should seek a person/group/place that best fits them and their needs.
I know I need to live within a budget, but I see things all the time I would love to get on the spot, but the way I cope is I remind myself I am on a budget, and if I really feel as if I want/need said item(s), I put them on a wish list and when I have enough money I go out and get the item(s). Though one of my friends is a compulsive shopper, and they sometimes don't have enough money for food, gas for their car, bills, rent, and even their college tuition. They had to drop out of school because their spending habits had gotten so bad that they no longer had enough money to pay their college. Seeing that happen is the exact reason why I try my hardest to stay on a budget for myself.