1. Patents. An action or procedure by which a third party can request a patent application’s refusal or an issued patent’s annulment. • Most countries allow opposition in some form.
2. Trademarks. A procedure by which a third party can contest an application to place a proposed trademark on the Principal Register before the placement occurs. Cf. CANCELLATION. [Cases: Trade Regulation 216. C.J.S. Trade-Marks, Trade-Names, and Unfair Competition §§ 181–182, 184–187.]