Category Killer

Category killer is a term used in marketing and strategic management to describe a product, service, brand, or company that has such a distinct sustainable competitive advantage that competing firms find it almost impossible to operate profitably in that industry. The existence of a category killer will eliminate almost all market entities, whether real or virtual. Many existing firms will leave the industry, thereby increasing the industry's concentration ratio.
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the name given to a retailer who specialises in a big way on a particular catagory of product; usually cutting the price e.g. Toys r Us, Pet Mart, Office World; it upsets 'traditional' retailers).