submarine patent
 n.— «Acacia is one of a number of companies that are making a good living by sitting on patents that are actually very general in their application. Individuals can register such patents, with no ability to develop associated product, wait for infringing products to appear, then get a good lawyer and go hunting. Such patents are sometimes referred to as submarine patents.» —“Patents and the threat to open source” by Robin Bloor The Register (U.K.) July 2, 2004. (source: Double-Tongued Dictionary)