Patent thicket
A technology covered by so many overlapping patents that nobody can ship a product without licences from a dozen owners at once.
The term was popularised by economist Carl Shapiro in his 2001 paper "Navigating the Patent Thicket". The problem is not any single patent but the sum: every holder can block, and anyone who wants to build has to negotiate with all of them. The smartphone became the textbook case. In 2011 a consortium including Apple and Microsoft paid 4.5 billion dollars for the patents of bankrupt Nortel, and in 2012 Google closed its 12.5-billion-dollar purchase of Motorola Mobility, largely for the patent portfolio.
The industry's usual remedy is the patent pool, in which owners bundle their patents and sell a single licence. That worked for H.264, but H.265 ended up with several competing pools and grew expensive enough that Google, Mozilla and others formed the Alliance for Open Media in 2015 and built the royalty-free AV1 instead.