refund
definition
to return money to a payer
example
When he wanted to return the unused t-shirt he had bought, the store refunded it fully without any trouble.
synonyms
pay backrepay
word origin — late Middle English (in the senses ‘pour back’ and ‘restore’): from Old French refonder or Latin refundere, from re- ‘back’ + fundere ‘pour’, later associated with the verb fund. The noun dates from the mid 19th century