N-COUNT 讨人厌者；有意搅扰他人者;（尤指）故意挑战权威者 If you refer to someone as a gadfly, you believe that they deliberately annoy or challenge other people, especially people in authority. 讨人厌者；有意搅扰他人者;（尤指）故意挑战权威者
It still remains to be seen whether Buchanan will be just a gadfly or a real threat to the president.