From Longman Business Dictionary
cashbackcash·back /ˈkæʃbæk/ noun [uncountableU]BANKING a way of getting cash from a SUPERMARKET (=a large shop selling food and other goods) when you are paying for your goods with a DEBIT CARD (=a plastic card made available by a bank that allows you to pay for goods and services, with the amounts taken immediately from your bank account)