a proceeding before the Trademark Trial and Appeal Board in which the plaintiff seeks to prevent the issuance of a registration of a mark. An opposition is similar to a proceeding in a federal court, but is held before the Trademark Trial and Appeal Board, a USPTO administrative tribunal.

Any person who believes that he or she will be damaged by the registration of a mark may file an opposition, but the opposition may only be filed in response to the publication of the mark in the Official Gazette.