I've seen this expression a few times in the Money forum, that does not seem to be nice , but I have no idea of what it is .

Anyone to help me ?

Thanks.

Let's say you sold something to a buyer on eBay. He paid you by Paypal. Buyer never received the item. He goes to Paypal and complain. You as seller did not fulfill all the requirements in the Paypal seller protection policy (e.g. you did not ship to a Paypal confirmed address - there's also other rules). Paypal will take the money out of your account to give back to the buyer. That's a reversal.

Financial term is rollback . That means the paypal will return the mony to the buyer.