Inter partes review

U.S. patent law
An inter partes review is a

"proceeding [that] allows anyone who is not the patent owner to request review of an issued patent by presenting prior art to PTO &mdash; either patents or other publications &mdash; to challenge the claimed invention's patentability as obvious or not novel. This review proceeding became available on September 16, 2012, 1 year after the enactment of the AIA, but entities cannot request this review until the later of (1) 9 months after a patent is granted or (2) completion of post-grant review, if such a proceeding is held."