Category Killer

Category Killer is a National retail chain that is dominant in its product category-usually by offering an extensive selection at low prices-to the point of killing smaller business players (putting them out of the business).
An example of a category killer business is eBay. As an online auction site, it has a monopoly. Another type of category killer business is the( Best Buy or toys "R" us) that is focused on one or few categories of merchandise and offers a wide selection of merchandise in these categories at relatively low prices.
Note: There is also a book named "Category Killers" written by Robert Spector in which he explores how Big Box retailers have come to overpower departmental stores, regional chains etc. He also discusses the societal and economic impact category killers have had on reshaping the retail industry.If u r interested, do read it.