Dump: To dispose of new product by selling it at or below cost. Most Hobby dealers purchase new product either directly from the manufacturer or through a wholesale distributor. Manufacturers often require that direct dealer accounts and/or distributors must purchase all products -- including those products dealers either do not want, or don't think they can sell -- in order to maintain their direct accounts. To liquidate this unwanted product, Hobby dealers sell it at a discount (dump it) if only to get it out of their inventory.
Throughout the late-90s and early-2000s, the internet (especially eBay) provided an avenue for dealers to dump unwanted new boxes. This was especially true of Pinnacle Brands and Fleer products.
The late-2000s/early-2010s saw the rise of the "wax jobbers," large internet-based retailers (like Dave & Adam's, Blowout Cards, and Atlanta Sportscards) with the ability to offer collectors lower prices on new product with their lower overhead and high volume. While not exactly practicing dumping, per se, the wax jobbers did threaten the traditional brick-and-mortar Hobby shops.
Beginning in 2011, Panini America started a Resale Price Maintenance (RPM) program known as MAPP (Minimum Advertised Price Program) to combat the (alleged) dumping problem and to keep the wax jobbers in check. Upper Deck also started a program on its own, but unlike Panini's MAPP, did not attempt to fix prices via RPM.