An Egg McFuckin Idiot is somebody or group of somebody's that are in line at a fast food restaurant, are together as a group or family with only one person ordering. They wait until they are right up at the register before they start deciding what they want to order, causing everybody behind them in line to wait while they stumble thru the rocket science process of trying to read the menu. It's even worse when they have kids that start to argue. Once the order is finally placed, the whole group lumbers away to find someplace to sit.
Frequently there is no established line at a fast food restaurant and it's not uncommon to get behind somebody, only to realize they aren't even in line. Or have the attendent ask the not next person inline for their order. No visit to a fast food restaurant is complete with experiencing an Egg Mcfuckin Idiot who gets up to the register with no fucking idea about what they want to eat. How many times do these morons have to visit a fast food restaurant before having some idea about the menu?