According to MPEP 2301.02, a contested case is defined as: "[A] Board proceeding other than an appeal under 35 U.S.C. 134 or a petition under § 41.3. An appeal in an inter partes reexamination is not a contested case." In simpler terms, a contested case is a proceeding before the Patent Trial and Appeal Board (PTAB) that involves disputes between parties, such as interference or derivation proceedings, but excludes regular patent appeals and certain petitions. To learn more: contested case PTAB patent interference derivation proceedings