A customer in any kind of retail establishment (restaurant, grocery, beauty salon, etc.), who seems to be committed to causing the greatest possible disruption to the orderly flow of business, but who isn't even aware that they are causing a problem. One thing that all NC's have in common, regardless of what type of retail business you meet one in, is that they consume far more of a staff person's time than can possibly be justified by the amount of money they will spend. Also, they will hold up the line for an inordinate amount of time, for everyone behind them, causing an ever-increasing level of impatience, eye-rolling, toe-tapping, and general disgust in the other customers, that will get dumped on the unfortunate staff person when the NC is finally done and the line starts moving again. Typical scenarios for Nightmare Customers are: recent immigrants with insufficient language skills to at least minimally communicate their needs to the store staff. Elderly customers, usually women, who are hard of hearing, possibly with early stage dementia, maybe also a recent immigrant with limited language skills, and for-sure also holding a purse stuffed with hundreds (thousands?) of coupons, mostly expired, that they are trying to use, but first have to find in the clutter.

When some little bitchboy is acting like a little tiny pee pee poo poo baby and messing up the group plans.