A term of hatred, or slur, designated to those who, when ordering fast food, order strictly from the cheaper list of items, known as the "Dollar Menu" in the case of McDonald's. Often, they order multiple items from said menu. Like many other slurs, the origin of this word is derived from its root words. The term is applied to those customers by the annoyed or disgruntled employees of the fast food establishment. Dollamus who order water as their beverage are particularly hated, especially if they attempt to order a "large water" (which most establishments do not provide) or a water without ice (which only shows how cheap they are). Dollamus who try to get sauce other than ketchup for their fries (such as bbq or sweet 'n' sour), or get unreasonably excessive sauces for their nuggets (like three cups for a 4-piece nugget) without paying the nominal surcharge are also reviled.
The dumbass dollamu ordered seven double cheeseburgers, five small fries, and also tried to get four "large waters" and a dozen cups of ranch sauce.