RACKS UP is a phrase that means to accumulate or gain something over time. The two crossword solutions for this phrase are INCURS (6 letters) and AMASSES (7 letters). INCURS means to become liable or responsible for something, while AMASSES means to gather or accumulate a large amount of something. Therefore, RACKS UP can be interpreted as gaining something over time, either through becoming liable for it or by gathering a large amount of it.