be dead beat
無敵的, 無法被打敗的. 看看前後文吧, 應該是這意思
beat a dead horse is an action that has no purpose, because no matter how hard...particular topic with no chance of affecting the outcome is beating a dead horse. beat a dead就是白費力氣,為什麼用dead horse...
be was/were been beat beat beaten become became become begin began begun...