When someone fills their shopping cart with more items than they have money for. Then when they get to the register they keep asking for the subtotal or removing items until the price comes down to whatever money they have. These people tend to have no regard for causing the line to back up a wasting inordinate amounts of time.
Jerry: This Lady is crazy. Her bill was $500. She's already removed enough items to bring it down to $100 and she STILL doesn't have enough money.
Alex: Yeah it's gonna take forever for it to be our turn. I hate when people go shopping a la cart!