definiens: shall mean, with respect to any IP Righ ts under the Seller IP, to contest the validity or enforceability of any such IP Rights, in whole or i n part, in any court, arbitration proceeding or oth er tribunal, including the United States Patent and Trademark Of fice, the European Patent Office, and the United St ates International Trade Commission . As used in this ter m, the term includes ( a ) fili ng an action under 28 U.S.C. § § 2201 - 2202 seeking a decla ration of invalidity or unenforceability of any suc h IP Rights ; ( b ) filing, or joining in, a petition under 35 U.S.C. § 311 to institute inter partes review of any such IP Rights, or any portion thereof ; ( c ) filing, or join ing in, a petition under 35 U.S.C. § 321 to institu te post - grant review of any such IP Rights, or any portion thereo f ; ( d ) any foreign equivalent of clauses ( a ), ( b ) o r ( c ) in any country outside of the United States ; or ( e ) filing or commencing any opposition, nullity or similar p roceedings challenging the validity of any such IP Rights in a ny country outside the United States ; but excludes ( i ) filing a request under 35 U.S.C. § 302 for re - examination of any such IP Rights, ( ii ) filing a request under 35 U.S.C. § 251 for a reissue of any such IP Rights, or ( iii ) a ny foreign equivalents of clause ( i ) or ( ii ) applic able in a country outside of the United States