Hi Nan! The full quote was “I have this friend at Bloomingdale's who's quitting tomorrow and he wants to abuse his discount”, right? The employees often have special discounts for the products their company makes. There are specific rules on how to use this discount (you can’t let your friends use it, for example). To abuse the discount means to violate/break the rules of using your employee discount. Below is also a story about discount abuse. Hope this helps!

Without context it's hard to be sure but I would guess this someone who has a discount maybe a staff discount for a particular business and is overusing it so, someone gets 10% off in the shop they work in and is buying everything their friends want at the discounted price