"Unsold copies" refers to the remaining, leftover or un-purchased items or editions of a specific product, usually referring to books, magazines, or other publications. These are the copies that were not bought or sold to customers. Full definition
The Booksellers Return Program ensures retailers that they can return unsold copies of your book for a complete refund. (archwaypublishing.com)
Of course, if we translate the story into the world of traditional print book publishing the publisher would merely have withdrawn the book from sale and requested retailers to return unsold copies for credit. (thefutureofpublishing.com)
She printed the first edition through a friend's publishing and vermicomposting company (Flower Press) in August 2002, figuring that she could always use unsold copies for worm bedding. (bookbrowse.com)