The credit card industry term for "refund."
Chargebacks are requested by merchants when the customer wants his or her money back from a credit card transaction. The credit card company deducts the specified amount from the cardholder's balance, and the merchant gives the cardholder a receipt (after getting a signature).
That said, credit card companies do not like chargebacks. Why? Customer service costs money, and credit card issuers don't like to waste money. Merchants with a high rate of chargebacks (think porn web sites) will eventually draw the wrath of Visa, Mastercard, American Express, and Novus (Discover). Many of these merchants lose their accounts and become unable to take credit cards, or are assessed much higher processing fees to atone for their high chargeback rates.