What is Merchant Account Provider?

Legal Definition
Merchant account providers give businesses the ability to accept debit and credit cards in payment for goods and services. This can be face-to-face, on the telephone, or over the internet.

Credit cards have become the preferred method of payment in today's market, making a merchant account essential for most businesses.
-- Wikipedia
Legal Definition
Bank or other financial institution that has merchant account services for traders. Processing onsite and online credit card and electronic-commerce transactions for a fee and/or the right to collect on the credit card debt owed by the buyer are examples of these services. In the US, also known as merchant bank.