IPA: //ˈkæʃbæk//
KK: /ˈkæʃbæk/
A percentage of money returned to a customer after making a purchase, often used as an incentive by credit card companies or retailers.
I received a cashback reward after buying my new phone.
Cashback is formed from "cash" (from Middle English *cashe*, meaning money in the form of coins or notes) and "back" (meaning return). The term refers to the return of a portion of money spent, typically in a transaction or purchase.
Think of receiving money 'back' after spending 'cash' — that's what cashback means.