An organization that uses its patents to generate revenue without manufacturing the products that the patents pertain to. The patents are often purchased from a third party, which may be bankrupt or no longer interested in bringing the product to market.
Also called a "non-practicing entity" (NPE) or "patent assertion entity" (PAE), which are less denigrating, the patent troll looks for infringers that have invested heavily in the product and often has to threaten them with or actually instigate a lawsuit in order to obtain licensing revenues. Companies that are involved in the business that the patent covers may indeed sue others for patent infringement, but that does not make them a patent troll. A patent troll is a holding company that buys patents based on their potential profitability if enforced. See Internet troll