Within the USPTO, Opposition Proceedings are legal mechanisms whereby an individual, or entity, that feels a trademark application should not be allowed to mature to registration, may file an action to stop oppose registration of said application. These proceedings may be quite comprehensive and tend resemble litigation of trademark matters within the United States Federal Court System.
Also within the USPTO, Cancellation Proceedings are legal mechanisms whereby an individual, or entity, that feels a trademark registration should be cancelled for good cause, may file an action to cancel said registration. Once again, in much the same manner as Opposition Proceedings, these proceedings are quite comprehensive and tend resemble litigation of trademark matters within the United States Federal Court System.
These proceedings are filed within The Trademark Trial and Appeal Board (TTAB) of the USPTO, which is an administrative board that possesses jurisdiction over such matters as appeals from decisions of the Trademark Office and opposition/cancellation proceedings.