The phrase "cash the barrelhead" is a term that refers to an immediate payment made for goods or services without any form of credit or delay. While this phrase may be commonly used in certain regions, there are several synonyms that can be used in place of it. Some of these synonyms include paying on the spot, paying in cash, paying upfront, making immediate payment, paying cash on delivery, and paying in advance. These phrases all imply the same concept of prompt payment without any form of credit or delayed payment. So, the next time you need to make a payment on the spot, consider using one of these synonyms to describe your intentions.